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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
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↗
PubMed2001

Medical knowledge reengineering--converting major portions of the UMLS into a terminological knowledge base.

We describe a semi-automatic knowledge engineering approach for converting the human anatomy and pathology portion of the UMLS metathesaurus into a terminological knowledge base. Particular attention is paid to the proper representation of part-whole hierarchies, which complement taxonomic ones as a major hierarchy-forming principle for anatomical knowledge. Our approach consists of four steps. First, concept definitions are automatically generated from the metathesaurus, with LOOM as the target language. Second, integrity checking of the emerging taxonomic and partonomic hierarchies is automatically carried out by the terminological classifier. Third, terminological cycles and inconsistencies are manually eliminated and, in the last step, the knowledge base built this way is incrementally refined by a medical expert. Our experiments were run on a terminological knowledge base which is composed of 164,000 concepts and 76,000 relations. Empirical evidence for the lack of logical consistency, adequacy and improper granularity of the UMLS knowledge source is given, and finally, assessments of what kind of efforts are needed to render the formal target representation structures complete and empirically adequate.

Anatomy↗
PubMed2001

New strategies in platelet inhibition in noncoronary interventions.

Thrombembolic complications frequently occur during and after endovascular procedures because of associated arterial injury and thrombotic characteristics of implanted devices such as stents. New strategies in platelet aggregation inhibition are now available blocking the final and common pathway of platelet aggregation, the glycoprotein IIb/IIIa receptor. This treatment modality seems to be more effective for prophylaxis and prevention of thrombembolic complications than standard antiplatelet therapy. Most of the data provided for glycoprotein IIb/IIIa receptor blockade are derived from studies of coronary interventions. This report reviews the pharmacodynamic differences of classic and new drugs for platelet inhibition and the basic considerations for antiplatelet therapy in noncoronary interventions.

Arteries↗
PubMed2001

[Endovascular therapy of renal artery stenosis: technical results with the Palmaz-Corinthian stent].

OBJECTIVE: To evaluate the technical performance and delivery characteristics of the Palmaz-Corinthian stent for endovascular therapy of atherosclerotic renovascular disease. METHODS: 61 patients underwent implantation of 76 Palmaz-Corinthian (PC) stents in 72 arteries. 50 original PC and 26 PC stents with the modified IQ-design were employed. The indications comprised primary stenting of ostial (n = 49) or truncal (n = 1) stenosis or occlusion (n = 3), and selective stenting following complicated (dissection, n = 4) or unsuccessful (n = 8) angioplasty. The remaining stents were placed in patients with recurrent stenosis (n = 5) or acute aortic dissection (n = 2) involving the renal artery. Mean severity and length of stenosis were 81.3% and 9.8 mm, respectively. 39 lesions were rated eccentric or calcified. Data on technical success, complication rate, delivery characteristics and ease of placement compared to standard renal stents were retrieved from a prospective multicenter registry. RESULTS: Stent delivery was successful in all patients, major complications were not reported. Stent placement was suboptimal in 7 of 72 cases: 4 stents were located too distally in the renal artery, necessitating proximal coaxial overstenting in 2 cases. The distal part of the stenosis was incompletely covered and the orifice of a segmental branch inappropriately overstented in one case each. One stent was dislodged from the balloon, resulting in stent protrusion in the aortic lumen. Significant residual stenosis after stenting was not observed. Overall stent deliverability, trackability and potential repositioning inside the stenosis were rated positive, radio-opacity was rated superior for the IQ design. CONCLUSION: Technical performance and delivery characteristics of the Palmaz-Corinthian stent have been significantly improved compared to the Palmaz design, allowing mostly correct placement in renal artery stenoses with a low complication rate.

Angiography, Digital Subtraction↗
PubMed2001

[2D-phase contrast flow evaluation and contrast-enhanced MR angiography for perioperative assessment of internal mammary artery grafts].

PURPOSE: To evaluate LV functional parameters, graft flow and patency in patients with IMA grafts using a combined MR protocol with phase-contrast technique and contrast enhanced MR angiography. MATERIAL AND METHODS: Using a 1.5 T MR system 27 patients with 27 left internal mammary artery (LIMA) and 41 venous grafts were examined before and 6 months after CABG surgery. A T(1)w-TSE sequence (slice thickness 5 mm) was applied for morphological imaging. LV function (EF, CO) was evaluated on cine images (segmented FLASH 2D, TR(eff) 11 ms, TE 4.8 ms, flip angle 25 degrees ). A phase-contrast FLASH 2D (TR 24 ms, TE 5 ms, flip angle 20 degrees ) sequence was applied for aortic and IMA flow measurements. Postoperatively, a contrast enhanced FLASH 3D MR angiography (TR 3.8 ms, TE 1.4 ms, flip angle 30 degrees ) with 25 ml Gd-DTPA was performed to assess bypass patency. RESULTS: In patients with reduced LV function (ejection fraction < 50 %) an improvement of the ejection fraction from 38.4 +/- 10.3 % to 49.8 +/- 15.3 % (p < 0.05) was found postoperatively. LIMA grafts were occluded in 1/27 patients, while 6/41 venous grafts were occluded. Distal LIMA anastomoses were demonstrated in 33 % by MRA. Flow of LIMA decreased from 21.2 +/- 11 ml/min/m(2) preoperatively to 14.4 +/- 9.6 ml/min/m(2) postoperatively (p < 0.01). CONCLUSION: MR imaging allows accurate combined assessment of LV function, bypass patency and flow. The protocol of this study may be applicable for perioperative follow-up studies in patients after CABG surgery.

Aged↗
PubMed2001

[Multidetector CT Angiography - is it a valuable screening tool to detect significant renal artery stenosis?].

PURPOSE: To evaluate the diagnostic value of multidetector CT angiography (MDCTA) of the renal arteries. METHODS: 27 patients underwent MDCTA of the renal arteries. Scan parameters were: collimation 4 x 1 mm, pitch 1.5, effective slice thickness 1.25 mm, reconstruction increment 0.8 mm, circulation time measurement, power injection of 80 ml iomeprol 400, flow 4 ml/sec. Independent reading on laser film was done by two radiologists using edited maximum intensity projections, multiplanar reconstructions and source images. Standard of reference was a 3D-FLASH MR angiography (1.5 T, 3.9/1.2, 10 degrees 0.2 mmol GdDTPA/kg bw) in 10 and intraarterial angiography in 17 patients. RESULTS: Analysing 63 arteries, sensitivity, specificity, positive predictive value and negative predictive value in terms of detection of moderate and high grade renal artery stenosis (n = 10) were 90, 98, 90 and 98 % for reader A, and 90 % each for reader B, respectively (kappa = 0.91 interobserver agreement). 1/11 accessory renal arteries was missed by both angiography and MDCTA. Image quality was graded as excellent or good in 26/27 of cases by both readers. CONCLUSION: MDCTA proved to be a highly accurate tool in the detection of therapeutically relevant renal artery stenosis.

Aged↗
PubMed2001

Peripheral artery occlusion: treatment with abciximab plus urokinase versus with urokinase alone--a randomized pilot trial (the PROMPT Study). Platelet Receptor Antibodies in Order to Manage Peripheral Artery Thrombosis.

PURPOSE: To evaluate the combination of a platelet glycoprotein IIb/IIIa complex receptor inhibitor and urokinase for treatment of recent (<or=6 weeks) arterial occlusion of the legs. MATERIALS AND METHODS: Seventy patients with lower extremity arterial occlusion of less than 6 weeks duration were randomly separated into two treatment groups: urokinase plus abciximab or urokinase plus placebo. Primary end points were the rate of major complications at 30 days after randomization and the rates of amputation-free survival and survival without open surgery or major amputation at follow-up of 90 days. Two readers unaware of the patients' treatment group assignments analyzed digital subtraction angiograms as they related to the study end points, with a final consensus reading. RESULTS: Thrombolysis relative to clot length was faster in the urokinase-plus-abciximab group (odds ratio, 0.52; 95% CI: 0.35, 0.76; P < .001). There were no procedure-related deaths or intracranial hemorrhages, but the rate of nonfatal major bleeding was higher with urokinase plus abciximab (four of 50 patients) than with urokinase alone (none of 20 patients; P = .32). At 90 days, amputation-free survival was 96% (48 of 50 patients) in the urokinase-plus-abciximab group compared with 80% (16 of 20 patients) in the urokinase alone group. The hazard ratio for the two Kaplan-Meier curves was 0.42 (95% CI: 0.16, 0.96; P = .04). CONCLUSION: In patients with lower extremity arterial occlusion who were undergoing urokinase thrombolysis, adjunctive abciximab treatment resulted in faster thrombus dissolution and improved amputation-free survival, despite an increase in major bleeding.

Abciximab↗
PubMed2001

Fluorescence correlation spectroscopy as a new method for the investigation of aptamer/target interactions.

Fluorescence correlation spectroscopy is an attractive tool for monitoring molecular interactions in solution. We report here a new and highly sensitive method for studying the interaction of aptamers with their targets using this technique. In vitro selection technology is a combinatorial method for the generation of nucleic acid receptors (aptamers) that are capable of binding to various target molecules. Using the in vitro selection approach we isolated RNAs which bind to the antibiotic moenomycin with high affinity. The formation of RNA-moenomycin complexes was studied by fluorescence correlation spectroscopy with a tetramethylrhodamine-labeled derivative of moenomycin.

Combinatorial Chemistry Techniques↗