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Biomedical subjects

U Hahn

Publications and source records attributed to U Hahn.

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

Isolated coronary artery rupture after blunt chest trauma.

After blunt chest trauma, a patient with chronic coronary heart disease sustained an isolated rupture of the right coronary artery. All findings suggested a heart contusion complicated by a non-compromising pericardial effusion and aggravated by anticoagulation with phenprocoumon. After right-ventricular failure occurred, emergency coronary revascularization could not prevent a fatal outcome. This case emphasizes that a coronary artery lesion may be considered in those cases of thoracic trauma with preexisting coronary calcification.

Aged↗
PubMed2003

Towards a broad-coverage biomedical ontology based on description logics.

We describe an ontology engineering methodology by which conceptual knowledge is extracted from an informal medical thesaurus (UMLS) and automatically converted into a formal description logics system (LOOM). Our approach consists of four steps: concept definitions are automatically generated from the UMLS, integrity checking of taxonomic and partonomic hierarchies is performed by LOOM's terminological classifier, cycles and inconsistencies are eliminated, as well as incremental refinement of the evolving knowledge base is performed by a domain expert. We report on experiments with a very large knowledge base composed of 164,000 concepts and 76,000 relations.

Artificial Intelligence↗
PubMed2002

Multiple ionization of atom clusters by intense soft X-rays from a free-electron laser.

Intense radiation from lasers has opened up many new areas of research in physics and chemistry, and has revolutionized optical technology. So far, most work in the field of nonlinear processes has been restricted to infrared, visible and ultraviolet light, although progress in the development of X-ray lasers has been made recently. With the advent of a free-electron laser in the soft-X-ray regime below 100 nm wavelength, a new light source is now available for experiments with intense, short-wavelength radiation that could be used to obtain deeper insights into the structure of matter. Other free-electron sources with even shorter wavelengths are planned for the future. Here we present initial results from a study of the interaction of soft X-ray radiation, generated by a free-electron laser, with Xe atoms and clusters. We find that, whereas Xe atoms become only singly ionized by the absorption of single photons, absorption in clusters is strongly enhanced. On average, each atom in large clusters absorbs up to 400 eV, corresponding to 30 photons. We suggest that the clusters are heated up and electrons are emitted after acquiring sufficient energy. The clusters finally disintegrate completely by Coulomb explosion.

Journal Article↗
PubMed2002

Generation of GW radiation pulses from a VUV free-electron laser operating in the femtosecond regime.

Experimental results are presented from vacuum-ultraviolet free-electron laser (FEL) operating in the self-amplified spontaneous emission (SASE) mode. The generation of ultrashort radiation pulses became possible due to specific tailoring of the bunch charge distribution. A complete characterization of the linear and nonlinear modes of the SASE FEL operation was performed. At saturation the FEL produces ultrashort pulses (30-100 fs FWHM) with a peak radiation power in the GW level and with full transverse coherence. The wavelength was tuned in the range of 95-105 nm.

Journal Article↗
PubMed2002

[Unusual removal of a Küntscher nail after 35 years].

A 68 year old patient with persistent feeling of sickness and increasing pain in the left forearm was seen. A complex both bone fracture of the distal forearm shaft had been stabilized with Küntscher nails in radius and ulna 35 years ago. The loose ulna nail had been removed after ten weeks. Reosteosynthesis twelve months later with a Küntscher nail and cerclages had led to osteomyelitis and persistent bone defect, possibly caused by galvanic reaction between the different alloyies. A lymphocyte transformation test with nickel sulphate confirmed an allergic reaction and supported the indication to late implant removal. After exposure of the nail's end by a short approach a sufficient take over of power to the implant was reached by a coupling pole. Extraction was stopped after two centimetres by a blockage of the nail. Widening the entry of nail and drilling its whole notch by means of a Kirschner wire using the radiolucent ruler and by the repeated extraction and reinsertion led finally to the complete removal of the nail. Whereas local pain is disappeared three month after removal presenting bland local findings the general condition is improved slowly. Already Küntscher described the blockage of his nail after a short distance extraction. In addition to a number of not always successful means of extraction this method is described for the first time.

Adult↗
PubMed2002

[Cystic neck lymph node metastases as an indication of occult tonsillar carcinoma].

BACKGROUND: Cystic carcinomas of the neck without evidence of a primary tumor are diagnostically challenging lesions. Differentiation between a cystic lymph node metastasis of an occult primary tumor and a carcinoma arising in a branchiogenic cyst is frequently not possible even with histological examination. In order to clarify the diagnosis, an intensive search for a primary lesion in the upper aerodigestive tract must be carried out. DIAGNOSIS: An occult carcinoma might be situated in Waldeyer's ring, especially in the tonsillar crypts. These tumors tend to produce cystic metastases in the jugulodigastric region. Therefore, multiple biopsies have to be taken from the tissue of Waldeyer's ring. In the case of a positive histological result, adequate therapy of both the primary and the metastasis can be carried out. The diagnosis of a malignant branchiogenic cyst is only permissible after a primary lesion has been thoroughly excluded.

Aged↗
PubMed2002

[LISS versus condylar plate].

Up to the seventies the surgical treatment of supra- and bicondylar femoral fractures was difficult and showed a lot of complications. In most studies a conservative treatment was recommended. In the least 30 years the clinical outcome after surgical treatment improved. This was a result of the development of new implants and improved surgical techniques. However, today the primary surgical treatment is the therapy of choice. We reviewed from 1986 to 2001 n = 121 distal femoral fractures which were in 32 cases treated with a Condylar Blade Plate and in 10 cases with a less invasive stabilisation system (LISS). The final results after condylar blade plating were rated using the system that was described by Neer. The averaged follow up time was 9 years. Low postoperative infection rates and in 75% excellent and satisfactory results combined with low cost are the reference for the evaluation of the LISS results. While in our owen series according to the literature there were no significant better functional results for the LISS group than for the Condylar Blade Plate group there were only few autologous bone grafts necessary. Due to the angle-stable self-drilling and self-cutting screws and the Internal-Fixater Principle the LISS has some mechanical and biological edge on the condylar blade plate.

Bone Plates↗
PubMed2002

[Intramedullary fixation of pediatric bone shaft fractures].

Intramedullary stabilisation (Prévot-nailing) of shaft fractures in childhood allows full weight bearing without cast. Early fracture healing is seen by respecting soft tissue around fracture and by using distal or proximal approaches. Good indications of femoral shaft osteosynthesis are recommended in oblique- and transverse-fractures. Intramedullary stabilization seems to be a good alternative methode instead of casting calf-shaft-fractures. An instable fracture of forearm may be treated intramedullary to avoid often observed displacement ad axim and rotation. Humoral fractures primary have to be treated conservatively. Only in displaced fractures or in cases with additional injuries an intramedullary procedure with free range of motion is recommended.

Adolescent↗
PubMed2002

[Stabilizing intramedullary pediatric shaft fractures].

Intramedullary stabilisation (Prévot-nailing) of shaft fractures in childhood allows full weight bearing without cast. Early fracture healing is seen by respecting soft tissue around fracture and by using distal or proximal approaches. Good indications of femoral shaft osteosynthesis are recommended in oblique and transverse fractures. Intramedullary stabilization seems to be a good alternative method instead of casting calf-shaft fractures. An unstable fracture of forearm may be treated intramedullary to avoid often observed displacement ad axim and rotation. Humoral fractures primary have to be treated conservatively. Only in displaced fractures or in cases with additional injuries an intramedullary procedure with free range of motion is recommended.

Adolescent↗
PubMed2001

Molecular characterization of the 56-kDa CYP153 from Acinetobacter sp. EB104.

CYP153 a cytochrome P450 from Acinetobacter sp. EB104 catalyzes the hydroxylation of unsubstituted n-alkanes. We have decided to use the CYP153 system as a model for mechanistic studies on regioselective n-alkane oxidation and the interaction of hydrophobic substrates with soluble enzymes. Here the molecular cloning of the CYP153 gene is reported. Single specific primer PCR was applied to yield the whole gene sequence via chromosomal walks. CYP153 consists of 497 amino acids (M(r) = 56 kDa) and thus represents an unusually long bacterial P450, containing all P450 typical structural elements. It constitutes the new P450 family CYP153. The prolonged N-terminus of about 90 amino acids does not contain a so far known membrane-anchoring sequence but a 28-amino acid long amphipathic helix. The relevance of the remarkably long N-terminus and of other sequence motives like the hydrophobic F-G loop is discussed with respect to substrate binding and recognition.

Acinetobacter↗
PubMed2001

Novel biomarkers of the metabolism of caffeic acid derivatives in vivo.

The purpose of this study was to investigate biomarkers of the bioavailability and metabolism of hydroxycinnamate derivatives through the determination of the pharmacokinetics of their urinary elimination and identification of the metabolites excreted. Coffee was used as a rich source of caffeic acid derivatives and human supplementation was undertaken. The results show a highly significant increase in the excretion of ferulic, isoferulic, dihydroferulic acid (3-(4-hydroxy-3-methoxyphenyl)-propionic acid), and vanillic acid postsupplementation relative to the levels presupplementation. Thus, ferulic, isoferulic, and dihydroferulic acids are specific biomarkers for the bioavailability and metabolism of dietary caffeic acid esters. Isoferulic acid is a unique biomarker as it is not a dietary component, however, dihydroferulic acid may well derive from other flavonoids with a structurally related B-ring. 3-Hydroxyhippuric acid has also been identified as an indicator for bioavailability and metabolism of phenolic compounds, and shows a highly significant excretion increase postsupplementation. The results reveal isoferulic acid (and possibly dihydroferulic acid) as novel markers of caffeoyl quinic acid metabolism.

Adult↗
PubMed2001

Epicatechin and its in vivo metabolite, 3'-O-methyl epicatechin, protect human fibroblasts from oxidative-stress-induced cell death involving caspase-3 activation.

There is considerable current interest in the cytoprotective effects of natural antioxidants against oxidative stress. In particular, epicatechin, a major member of the flavanol family of polyphenols with powerful antioxidant properties in vitro, has been investigated to determine its ability to attenuate oxidative-stress-induced cell damage and to understand the mechanism of its protective action. We have induced oxidative stress in cultured human fibroblasts using hydrogen peroxide and examined the cellular responses in the form of mitochondrial function, cell-membrane damage, annexin-V binding and caspase-3 activation. Since one of the major metabolites of epicatechin in vivo is 3'-O-methyl epicatechin, we have compared its protective effects with that of epicatechin. The results provide the first evidence that 3'-O-methyl epicatechin inhibits cell death induced by hydrogen peroxide and that the mechanism involves suppression of caspase-3 activity as a marker for apoptosis. Furthermore, the protection elicited by 3'-O-methyl epicatechin is not significantly different from that of epicatechin, suggesting that hydrogen-donating antioxidant activity is not the primary mechanism of protection.

Antioxidants↗
PubMed2001

Diversity-based reasoning in children.

One of the hallmarks of inductive reasoning by adults is the diversity effect, namely that people draw stronger inferences from a diverse set of evidence than from a more homogenous set of evidence. However, past developmental work has not found consistent diversity effects with children age 9 and younger. We report robust sensitivity to diversity in children as young as 5, using everyday stimuli such as pictures of objects with people. Experiment 1 showed the basic diversity effect in 5- to 9-year-olds. Experiment 2 showed that, like adults, children restrict their use of diversity information when making inferences about remote categories. Experiment 3 used other stimulus sets to overcome an alternate explanation in terms of sample size rather than diversity effects. Finally, Experiment 4 showed that children more readily draw on diversity when reasoning about objects and their relations with people than when reasoning about objects' internal, hidden properties, thus partially explaining the negative findings of previous work. Relations to cross-cultural work and models of induction are discussed.

Adult↗
PubMed2001

Subacute myocardial infarction: assessment by STIR T2-weighted MR imaging in comparison to regional function.

PURPOSE: Increased T2 signal intensity (SI) can be regularly observed in myocardial infarction. However, there are controversial reports about the relationship of elevated T2 SI to myocardial viability and some authors propose that high T2 SI serves as a sign of irreversible myocardial injury. This study investigates increased T2 SI compared to myocardial function in patients with reperfused subacute myocardial infarction. Preserved function was used as criterion for viability. METHODS: Ten healthy volunteers and 17 patients with myocardial infarction and patent infarct related coronary artery were examined on a 1.5 T Magnetom Vision system (Siemens). For T2-weighted MR imaging a breath-hold STIR sequence with dark-blood preparation was used. Cine FLASH 2D imaging was applied to assess myocardial function. Signal-to-noise (S/N) in STIR T2 images was measured in normal and infarcted regions and subsequently identified by two independent observers. Based on a 20 segment model of the left ventricle findings were compared to regional myocardial function. RESULTS: Elevated STIR T2 SI was found in all 17 patients and observed in 27% (204/754) of segments. S/N of normal myocardium was 5.1 +/- 0.7 in volunteers and 4.9 +/- 0.8 in patients (P = NS). Infarcted myocardium presented with significantly increased S/N 12.8 +/- 1.9 (P < 0.0001). Significant transmural elevation of T2 SI was noted in 32% of segments with preserved systolic function. CONCLUSION: Increased STIR T2 SI can be observed transmurally in post-ischemic myocardial regions with preserved function. It therefore cannot be used as an exclusive marker for the non-viable region.

Aged↗
PubMed2001

[Diagnosis of intra-articular fracture of the head of the tibia. A prospective comparative study].

Complete visualization of the joint surface is essential for correct assessment of tibial head fractures. Conventional tomography, computed tomography (CT), and magnetic resonance imaging (MRI) are compared in this prospective study. We examined 27 patients (19 suffering from B fractures and 8 from C fractures) from 1 January 1995 to 11 November 1998. Conventional tomography underestimated the fractures in 3 of the 19 cases of B fractures. Computed tomography underestimated two of these cases. MRI could not exactly depict the essential structures in three of the eight cases of C fractures because of edema and effusions. MRI identified complete cruciate ligament rupture in 6 of the 27 cases (18%) and 10 meniscal ruptures in 9 cases (33%: 6 medial meniscus, 4 lateral meniscus). Complete ruptures of the lateral collateral ligament were detected in five cases and medial collateral ligament ruptures in two cases. According to this, 63% of the patients suffered from relevant accompanying soft tissue injuries. The rate of soft tissue injuries increased up to 92% including the partial collateral ligament ruptures. Local hospital conditions permitting, X-ray-loaded conventional tomography should no longer be used in tibial head fractures. X-ray-free MRI is most efficient in cases of B fractures, which can in most cases be treated with a minimum of invasive techniques. Computed tomography is to be used in cases of C fractures that are regularly managed by open surgery accompanied by direct visualization of the inside of the knee joint.

Adult↗
PubMed2001

Outpatient treatment of multiple myeloma with a combination of vincristine, Adriamycin and dexamethasone.

Patients with relapsed multiple myeloma (MM) have been shown to respond to a combination therapy consisting of vincristine, Adriamycin (doxorubicin) and high-dose dexamethasone (VAD). Because of the low hematological toxicity of the VAD regimen, this combination is frequently chosen for tumor reduction prior to high-dose therapy and blood stem cell transplantation. This study was designed to examine the efficacy and complications of outpatient VAD treatment. Over a period of 6 years, 103 outpatients with MM were treated with VAD chemotherapy administered by microprocessor-controlled infusion pumps via intravenous polyurethane catheters equipped with a safety valve. Response to treatment, treatment-associated complications and infections were documented and analyzed. In 85 of the 103 patients, tumor reduction by more than 25% was found. In 8 patients an occlusion occurred as a result of kinking of the central venous catheter in the subcutaneous segment. In two treatment cycles the infusions had to be stopped because of irreversible catheter occlusion. Twenty patients were hospitalized because of complications, which were infectious in 12 and noninfectious in 8. Severe infectious complications (> or =WHO grade III) occurred in 5.6% of the treatment cycles. Thus, continuous infusion of VAD over 96 h can be performed on an outpatient basis with a low complication rate.

Adult↗
PubMed2001

Aptamers that bind to the antibiotic moenomycin A.

Nuclease-resistant moenomycin-binding aptamers with dissociation constants in the range of 300 to 400 nM have been selected. Competition experiments have demonstrated that these aptamers recognize a disaccharide analogue of moenomycin. The results offer the opportunity of setting up a selective and sensitive assay for identifying moenomycin biosynthetic precursors.

Anti-Bacterial Agents↗