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Biomedical subjects

H Berger

Publications and source records attributed to H Berger.

At least 37 records · Page 2Linked to original sources
PubMed2003

Anomalous enhancement of the coupling to the magnetic resonance mode in underdoped Pb-Bi2212.

High-resolution angle-resolved photoemission with variable excitation energies is used to disentangle bilayer splitting effects and intrinsic (self-energy) effects in the electronic spectral function near the (pi,0) point of differently doped (Pb,Bi)(2)Sr(2)CaCu(2)O(8+delta). In contrast to overdoped samples, where intrinsic effects at the (pi,0) point are virtually absent, we find in underdoped samples intrinsic effects in the superconducting-state (pi,0) spectra of the antibonding band. This intrinsic effect is present only below the critical temperature and weakens considerably with doping. Our results give strong support for models which involve a strong coupling of electronic excitations with the resonance mode seen in inelastic neutron scattering experiments.

Journal Article↗
PubMed2003

Spectroscopic signatures of a bandwidth-controlled Mott transition at the surface of 1T-TaSe2.

High-resolution angle-resolved photoemission data show that a metal-insulator Mott transition occurs at the surface of the quasi-two-dimensional compound 1T-TaSe2. The transition is driven by the narrowing of the Ta 5d band induced by a temperature-dependent modulation of the atomic positions. A dynamical mean-field theory calculation of the spectral function of the half-filled Hubbard model captures the main qualitative feature of the data, namely, the rapid transfer of spectral weight from the observed quasiparticle peak at the Fermi surface to the Hubbard bands, as the correlation gap opens up.

Journal Article↗
PubMed2003

[Pseudoaneurysm of a subsegmental renal artery after percutaneous nephrolitholapaxy].

At postoperative day 10 of a percutaneous nephrolitholapaxy for a large stone in the right renal pelvis of a 78-year-old female patient, persistent gross hematuria, requiring blood transfusions, occurred. Selective renovasography showed a pseudoaneurysm of the branch of a segmental artery close to the lower renal calices. Subsequent selective placement of two "steel-coils" in the feeding artery through a coaxial catheter system resulted in complete and stable occlusion without loss of renal parenchyma. Thereafter, bleeding immediately stopped and the patient suffered no further complications. This tool of interventional radiology should be kept in mind before open surgery is considered.

Aged↗
PubMed2003

[Role of ORL1 receptors in the regulation of cardiac resistance to arrhythmogenic effects ].

It has been found that intravenous administration of nociceptin (0.4 mg/kg) prevents development of aconitine-induced arrhythmias but has no effect on the incidence of occlusion, reperfusion, CaCl2-induced arrhythmias, and exacerbates epinephrine-evoked dysrhythmias. Pretreatment with hexamethonium, atropine, guanethidine and naloxone did not abolish the arrhythmic effect of nociceptin. Intracerebroventricular infusion of orphanin FQ was shown to increase cardiac tolerance of arrhythmogenic influence of aconitine, but this effect is completely abolished by hexamethonium administration. It has been suggested that stimulation of both central and peripheral ORL1 receptors increases cardiac resistance against arrhythmogenic effect of aconitine via different mechanisms.

Aconitine↗
PubMed2002

Observation of an unconventional metal-insulator transition in overdoped CuO2 compounds.

The electron dynamics in the normal state of Bi(2)Sr(2)CaCu(2)O(8+delta) is studied by inelastic light scattering over a wide range of doping. A strong anisotropy of the electron relaxation is found which cannot be explained by single-particle properties alone. The results strongly indicate the presence of an unconventional quantum-critical metal-insulator transition where "hot" (antinodal) quasiparticles become insulating while "cold" (nodal) quasiparticles remain metallic. A phenomenology is developed which allows a quantitative understanding of the Raman results and provides a scenario which links single- and many-particle properties.

Journal Article↗
PubMed2002

Origin of the peak-dip-hump line shape in the superconducting-state (pi,0) photoemission spectra of Bi2Sr2CaCu2O8.

From detailed high-resolution measurements of the photon energy dependence of the (pi,0) superconducting-state photoemission spectrum of the bilayer Bi high-temperature superconductors, we show that the famous peak-dip-hump line shape is dominated by a superposition of spectral features originating from different electronic states which reside at different binding energies, but are each describable by essentially identical single-particle spectral functions. The previously identified bilayer-split CuO2 bands are the culprit: with the "superconducting" peak being due to the antibonding band, while the hump is mainly formed by its bonding bilayer-split counterpart.

Journal Article↗
PubMed2002

Fulminate intracardiac thrombosis associated with Budd-Chiari-syndrome and inferior vena cava thrombosis.

The most common cause of edema of the legs and dyspnea is congestive heart failure. Further differential diagnosis such as renal or hepatic failure have to be considered. We report the case of a previous healthy 65-year-old woman who developed dyspnea and massive edema of the legs followed by acute hepatic and renal failure. Imaging studies showed a thrombosis of the inferior vena cava (IVC) caused by a tumor between the right kidney and the IVC. Histological examination revealed a leiomyosarcoma of the IVC. Hepatic failure due to venous outflow obstruction (Budd-Chiari syndrome, BCS) was diagnosed. Coagulation profile showed a complex disorder due to acute hepatic failure. Factor V Leiden and prothrombin gene mutation G20210A could be excluded. The thrombosis extended from the femoral veins up to the right atrium. After 11 days of anticoagulation with heparin platelet counts decreased by more than 50%. Suspecting a heparin-induced thrombocytopenia the patient was placed on recombinant hirudin (lepirudin) for anticoagulation. Hepatic venogram showed a thrombosis of the hepatic vein orifices but not of the hepatic veins. The tumor and the thrombi were removed surgically. When the cardiopulmonary bypass was terminated new intracardiac thrombi occurred. Despite immediate surgical intervention the patient finally died due to right ventricular failure caused by the fulminate intracardiac thrombosis. In conclusion, thrombosis of the IVC may mimic congestive heart failure and may cause BCS. Neoplasms and coagulation disorders may cause thrombosis of the IVC.

Aged↗
PubMed2002

Indirect coronary angiography: a feasibility study.

The diagnostic method of choice to proof coronary artery disease and to localize stenoses and to judge the stage of the disease is coronary angiography. A new angiographic technique invented by. Wolffgram and Krieter that works without cannulation of the coronary arteries could simplify the interventional procedure. In addition, a technique like this could be used for angiography after CABG surgery directly on the table for quality assurance reasons. This angiography could be performed by the cardiac surgeon without necessarily involving a cardiologist. A feasibility study was successfully done in a cooperation of the Departments. for Cardiology and Cardiac Surgery, Munich University, Steinbeis Transfer Centre for rHealthcare Technologies, Tuebingen and Fraunhofer Technology Development Group (TEG), Stuttgart.

Animals↗
PubMed2001

Spectroscopic indications of polaronic carriers in the quasi-one-dimensional conductor (TaSe4)2I.

Angle-resolved photoemission (ARPES) on the quasi-one-dimensional conductor (TaSe4)2I shows a hidden Fermi-surface crossing in its metallic state and the opening of a Peierls gap at low temperatures. The underlying quasiparticles have vanishing spectral weight and extremely short coherence lengths. They are interpreted as polarons in the strong-coupling adiabatic limit, and almost all their ARPES weight is incoherent. These observations suggest a scenario where the long-standing contradictions between ARPES and other experiments on Peierls materials could be resolved.

Journal Article↗
PubMed2001

Structural evidence for Ta-tetramerization displacements in the charge-density-wave compound (TaSe4)2I from x-ray anomalous diffraction.

We use the anomalous x-ray diffraction technique to investigate the nature of the tantalum displacement pattern in the modulated phase of the charge-density-wave compound (TaSe4)2I. In addition to the known acousticlike modulation, we find the first direct evidence for the condensation of opticlike Ta displacements along the metallic chains corresponding to an LLSS pattern of long and short in-chain Ta-Ta distances (Ta-tetramerization modes). This result confirms a previous model in which the interaction of the electronically coupled optic modes with long-wavelength acoustic shear modes leads to the condensation of a modulation of mixed character.

Journal Article↗
PubMed2001

Charge dynamics of 2H- TaSe2 along the less-conducting c-axis.

We present an optical study of 2H-TaSe2 along the less conducting c-axis. This dichalcogenide compound belongs to a large class of conductors called "bad metals" (with a mean free path smaller than the lattice constant along the c-axis), which also includes the superconducting cuprates. The optical response shows the progressive development of a pseudogaplike feature with decreasing temperature. The spectral weight lost by the opening of such a pseudogap goes into the narrow Drude component, developing at low frequency and temperature. There is no violation of the sum rule in 2H-TaSe2 contrary to the cuprates.

Journal Article↗
PubMed2001

[Hemosuccus pancreaticus (bleeding into the pancreatic duct). A rare complication of pancreatitis].

HISTORY AND ADMISSION FINDINGS: A 41-year-old man was admitted because of recurrent tarry stools and dizziness. Chronic pancreatitis induced by alcoholism was known. The main abnormal laboratory finding was anaemia (haemoglobin 4.6 g/dl, erythrocytes 2.28/fl). INVESTIGATIONS, TREATMENT AND COURSE: At endoscopy of the oesophagus, stomach and duodenum, fresh blood was found in the duodenum, a small trickle of blood coming from the papilla of Vater. Endoscopic retrograde cholangiography discovered no abnormality in the biliary system. Selective contrast imaging of the pancreatic duct demonstrated a short prepapillary stenosis and a prestenotic dilatation (up to 15 mm diameter) of the pancreatic duct with a cloudy contrast filling defect. After catheter withdrawal from the pancreatic duct blood spurted from the papilla. Emergency angiography revealed pseudoaneurysmatic dilatation of the gastroduodenal artery in the region of the head of the pancreas. At selective catheterization this artery was successfully occluded with metal coils placed both proximally and distally to the source of bleeding. CONCLUSION: Gastrointestinal bleeding is a rare but potentially life-threatening complication of pancreatitis. When searching for bleeding in the upper gastrointestinal tract, the papilla of Vater should be looked for as a possible source. Bleeding from the pancreas occurs particularly in pancreatitis, pancreatic pseudocyst or pancreatic tumour.

Adult↗
PubMed2001

Silent cerebral infarction: risk factor for stroke complicating carotid endarterectomy.

"Silent" cerebral infarction is found in 20% to 30% of patients with significant internal carotid artery (ICA) disease. Our purpose was to determine whether such "silent" cerebral infarction in the operated carotid territory represents a risk factor for stroke during and immediately after carotid endarterectomy. Over 5 years we followed a cohort of 663 patients with symptomatic and asymptomatic ICA stenosis who were consecutively scheduled for surgery. The stenosis was more than 70% in patients with transient ischemic attacks and more than 95% in asymptomatic stenosis patients. All patients underwent preoperative computed tomography to determine the frequency, extent, and location of any "silent" cerebral infarction. Patients were grouped by the absence or presence of infarction in the operated carotid territory. Among the entire cohort, 20 patients had a major perioperative stroke (3.0%). All deaths were stroke-related. No intracranial bleeding occurred. Major stroke occurred in four (0.8%) patients without appropriate "silent" cerebral infarction, compared with 16 (8.8%) with an appropriate "silent" cerebral infarct (p < 0.001). After adjustment for confounding co-variables (e.g., gender, presence of preoperative symptoms, and age), "silent" cerebral infarction was found to be the only independent predictor of perioperative major stroke for symptomatic and asymptomatic stenosis (overall adjusted relative risk 11.5, 95% confidence interval 3.8-34.9, p < 0.0001). Patients with "silent" cerebral infarction seem to be at increased risk of perioperative stroke. Consequently, preoperative cerebral imaging is important for risk classification.

Aged↗
PubMed2001

Relationship between DNA ploidy-related parameters and the deletions in mismatch repair genes MLH1 and MSH2 in lentigo maligna and malignant melanomas.

Defects in DNA mismatch repair genes MLH1 and MSH2, first described in hereditary nonpolyposis colon cancer (HNPCC), have been postulated to be responsible for malignant transformation in several tumours. To date there are no data on cutaneous tumours. Using a PCR assay it was possible to identify deletions in MSH2 (exonic regions 12 and 13) in 16 of 47 lentigos maligna and in 10 of 36 malignant melanomas. Deletions in MLH1 (exonic regions 15 and 16) were found in 11 of 47 lentigos and in 15 of 36 melanomas. Comparison of DNA ploidy-related parameters between lentigos with and without exonic deletions in MSH2 and MLH1 did not show any significant differences. In contrast, melanomas positive and negative for exons 12 and 13 (MSH2) (26/36 and 10/36, respectively) differed significantly with respect to the percentages of diploid cells (P = 0.0179) and tetraploid cells (P = 0.0042). Comparison of melanomas positive and negative for exons 15 and 16 (MLH1) (21/36 and 15/36, respectively) showed significant differences in the percentage of aneuploid cells between 2c and 4c (P = 0.0141) and tetraploid cells (P = 0.0404). In summary, deletions in DNA mismatch repair proteins MSH2 and MLH1 were present both in lentigo maligna and in melanomas and correlated with DNA ploidy-related parameters in malignant melanomas.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Inhibitory action of nociceptin/orphanin FQ on functionally different thalamic neurons in urethane-anaesthetized rats.

1. In this study we administered nociceptin/orphanin FQ (NC) ionotophoretically onto neurons located in functionally distinct thalamic structures of urethane-anesthetized rats. Extracellular single unit recordings were made in the medial and lateral ventroposterior nucleus, posterior thalamic nucleus, zona incerta, lateral posterior nucleus, laterodorsal nucleus, ventrolateral nucleus and reticular nucleus. 2. NC decreased the firing rate in 60% of thalamic neurons. This decrease in firing rate was accompanied by a significant reduction in the number of high threshold bursts. 3. In about 20% of the neurons NC increased the firing rate. In most cells NC-induced increases in discharge rate could be blocked by the GABA(A) receptor antagonists bicuculline and SR 95531. 4. The NC receptor ligands [Phe(1)Psi(CH(2)-NH)Gly(2)] nociceptin(1-13)NH(2), Ac-RYYRIK-NH(2) and [Nphe(1)]NC(1-13)NH(2) were also evaluated. All these peptides inhibited NC-induced changes in firing rate. In addition, in some neurons where NC inhibited firing, [Nphe(1)]NC(1-13)NH(2) and Ac-RYYRIK-NH(2) elicited per se an increase in firing rate, suggesting the existence of tonic innervation of thalamic neurons by NC-containing fibres. 5. In NC-inhibited neurons nocistatin induced a significant increase in firing rate. 6. The present study demonstrated that NC regulates various thalamic nuclei related not only to somatosensory, but also to the visual and motor functions.

Action Potentials↗
PubMed2001

Life-threatening gastrointestinal bleeding due to a jejunal lesion of Henoch-Schönlein purpura.

The case of a 56-year-old patient with Henoch-Schönlein purpura (HSP) and fulminant gastrointestinal bleeding is reported. The patient was admitted to hospital because of palpable purpura on both legs, painful joints and diffuse abdominal pain. Suspected HSP was histologically proven and treated with prednisolone. Despite recovery, acute gastrointestinal bleeding, with melena and a drop in hemoglobin concentration from 11.2 to 4.2 g/dl, occurred 30 days after medication was started. Immediate endoscopic examination of the upper gastrointestinal tract showed no signs of bleeding whereas colonoscopy showed fresh blood and blood clots in the terminal ileum and the colon. Since the bleeding source could not be detected endoscopically, mesenteric angiography was performed, demonstrating active bleeding from a jejunal artery. Thereafter the bleeding source was located by intraoperative peroral enteroscopy and treated by resection of a short segment of jejunum.

Gastrointestinal Hemorrhage↗