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Biomedical subjects

P Steiner

Publications and source records attributed to P Steiner.

At least 19 recordsLinked to original sources
PubMed2005

Austrian experiences with redo antireflux surgery.

BACKGROUND: From 1996, the entire number of fundoplications performed in Austria increased dramatically, favoring the laparoscopic technique. Despite good results, some patients experience failure of antireflux surgery and therefore require redo surgery if medical therapy fails to control symptoms. The aim of the study was to describe the refundoplication policy in Austria with evaluation of the postoperative results. METHODS: A questionnaire was sent to all Austrian surgical departments at the beginning of 2003 with questions about redo fundoplications (number, techniques, intraoperative complications, history, migration of patients, preoperative workup, mortality, and postoperative long-term complaints). It also included questions about primary fundoplications (number, technique, postoperative symptoms). RESULTS: Out of 4,504 primary fundoplications performed in Austria since 1990, 3,952 have been carried out laparoscopically. In a median of 31 months after the primary operation, 225 refundoplications have been performed, laparoscopically in the majority of patients. The Nissen and the partial posterior fundoplication were the preferred techniques. The conversion rate in these was 10.8%, mainly because of adhesions and lacerations of the spleen, the stomach, and the esophagus. The mortality rate after primary fundoplications was 0.04%, whereas the rate after refundoplications was 0.4%, all resulting from an open approach. CONCLUSION: Laparoscopic refundoplications are widely accepted as a treatment option after failed primary antireflux surgery in Austria. However, the conversion rate is 6 times higher and the mortality rate is 10 times higher than for primary antireflux surgery. Therefore, redo fundoplications should be performed only in departments with large experience.

Austria↗
PubMed2004

Design and validation of a tool for neurite tracing and analysis in fluorescence microscopy images.

BACKGROUND: For the investigation of the molecular mechanisms involved in neurite outgrowth and differentiation, accurate and reproducible segmentation and quantification of neuronal processes are a prerequisite. To facilitate this task, we developed a semiautomatic neurite tracing technique. This article describes the design and validation of the technique. METHODS: The technique was compared to fully manual delineation. Four observers repeatedly traced selected neurites in 20 fluorescence microscopy images of cells in culture, using both methods. Accuracy and reproducibility were determined by comparing the tracings to high-resolution reference tracings, using two error measures. Labor intensiveness was measured in numbers of mouse clicks required. The significance of the results was determined by a Student t-test and by analysis of variance. RESULTS: Both methods slightly underestimated the true neurite length, but the differences were not unanimously significant. The average deviation from the true neurite centerline was a factor 2.6 smaller with the developed technique compared to fully manual tracing. Intraobserver variability in the respective measures was reduced by a factor 6.0 and 23.2. Interobserver variability was reduced by a factor 2.4 and 8.8, respectively, and labor intensiveness by a factor 3.3. CONCLUSIONS: Providing similar accuracy in measuring neurite length, significantly improved accuracy in neurite centerline extraction, and significantly improved reproducibility and reduced labor intensiveness, the developed technique may replace fully manual tracing methods.

Animals↗
PubMed2004

Pharmacokinetics of ethambutol in children and adults with tuberculosis.

SETTING: Five hospitals in the United States. OBJECTIVE: To describe ethambutol pharmacokinetics in children and adults with active tuberculosis (TB). DESIGN: Prospective, open-labeled study in 56 adults and 14 children with active tuberculosis who received ethambutol as part of their multidrug TB regimens. RESULTS: Most serum samples were collected up to 10 h post dose and assayed using a validated gas chromatography assay with mass selective detection (GC/MS). Concentration data were analyzed using non-compartmental and population pharmacokinetic methods. Drug exposure increased with dose, but less than proportionally at doses >3000 mg. Lower than expected maximum serum concentrations (Cmax <2 microg/ml) were common in adults. Very low Cmax (<1 microg/ml) were common in children, as was delayed absorption (time to Cmax >3 h). Many Cmax were at or below typical TB minimal inhibitory concentrations. Cmax values for HIV-positive patients were 20% lower than HIV-negative patients with daily doses, but were similar with larger twice-weekly doses. CONCLUSIONS: Adult TB patients often had lower than expected ethambutol serum concentrations, and most pediatric TB patients had very low ethambutol serum concentrations. Higher doses and therapeutic drug monitoring may be indicated for many of these patients.

Absorption↗
PubMed2003

Overexpression of the ATP-dependent helicase RecG improves resistance to weak organic acids in Escherichia coli.

Increased resistance to several weak organic acids was conferred on Escherichia coli by overexpression of the ATP-dependent helicase RecG and, to a lesser extent, by overexpressing the helicase RuvAB. This property of helicases was identified by reproducible selection of recG-bearing clones from genomic libraries of the acetate-resistant species Acetobacter aceti and Staphylococcus capitis. We show that overexpression of RecG from both species, but also from E. coli, increased the maximum biomass concentration attained by E. coli cultures that were grown in the presence of various weak organic acids and uncouplers. Furthermore, overexpression of RecG from A. aceti significantly improved the maximum growth rates of E. coli under weak organic acid challenge. Based on the known role of RecG in DNA replication/repair, our data provide a first indication that weak organic acids negatively affect DNA replication and/or repair, and that these negative effects may be counteracted by helicase activity.

Acetobacter↗
PubMed2003

Interactions between synaptic vesicle fusion proteins explored by atomic force microscopy.

Measuring the biophysical properties of macromolecular complexes at work is a major challenge of modern biology. The protein complex composed of vesicle-associated membrane protein 2, synaptosomal-associated protein of 25 kDa, and syntaxin 1 [soluble N-ethyl-maleimide-sensitive factor attachment protein receptor (SNARE) complex] is essential for docking and fusion of neurotransmitter-filled synaptic vesicles with the presynaptic membrane. To better understand the fusion mechanisms, we reconstituted the synaptic SNARE complex in the imaging chamber of an atomic force microscope and measured the interaction forces between its components. Each protein was tested against the two others, taken either individually or as binary complexes. This approach allowed us to determine specific interaction forces and dissociation kinetics of the SNAREs and led us to propose a sequence of interactions. A theoretical model based on our measurements suggests that a minimum of four complexes is probably necessary for fusion to occur. We also showed that the regulatory protein neuronal Sec1 injected into the atomic force microscope chamber prevented the complex formation. Finally, we measured the effect of tetanus toxin protease on the SNARE complex and its activity by on-line registration during tetanus toxin injection. These experiments provide a basis for the functional study of protein microdomains and also suggest opportunities for sensitive screening of drugs that can modulate protein-protein interactions.

Antigens, Surface↗
PubMed2003

Heparanase-1 gene expression in normal, hyperplastic and neoplastic prostatic tissue.

Heparanase-1 (Hpa-1) has been implicated in tumour invasion and metastasis. In the present study, we evaluated the clinicopathological significance of Hpa-1 mRNA expression in prostate cancer and non-cancerous prostatic tissue by one-step polymerase chain reaction (PCR) of laser microdissected prostatic gland cells. In addition, cell type-specific expression of Hpa-1 mRNA in prostatic tissue was analysed by in situ hybridisation. Hpa-1 mRNA expression was found in 50% of normal and 40% of hyperplastic prostatic tissue. In situ hybridisation showed that Hpa-1 mRNA was strongly expressed in prostate gland cells. Of the 26 prostate carcinomas tested, 42% were positive for Hpa-1 mRNA. However, in non-cancerous prostatic tissue, Hpa-1 mRNA was significantly more often expressed than in less differentiated or more invasive prostate cancers (P<0.05). In situ hybridisation revealed only focal Hpa-1 mRNA expression in the neoplastic gland cells. Hpa-1 mRNA expression in the tumours significantly correlated with tumour differentiation and tumour stage (P<0.05). Our data indicate that Hpa-1 gene expression may be lost during dedifferentiation of prostatic gland cells.

Adult↗
PubMed2003

[Comparison of an edema-sensitive HASTE-TIRM sequence with delayed contrast enhancement in acute myocardial infarcts].

GOAL: Comparison between a fluid-sensitive (HASTE-TIRM)-sequence and delayed contrast-enhancement in patients with acute myocardial infarct (AMI) in MRI. MATERIAL AND METHODS: 32 patients with AMI were imaged 7 +/- 4 days after the time of infarction with a 1.5 T unit using a T2 HASTE-TIRM and a contrast-enhanced (CE) T1 turbo FLASH sequence. A threshold method (>2 SD in comparison with normal myocardium) was used to quantify the hyperintense zones in both sequences. The transmurality of the hyperintense regions was measured on a segmental basis. RESULTS: The hyperintense areas were larger on the HASTE-TIRM sequence with 29.6 +/- 13.2 % of the left ventricular (LV) area as compared to the CE-MRI with 19.2 +/- 10 % of the LV area (p < 0.0001). The measured transmurality was higher with the HASTE-TIRM sequence than with the CE-MRI (p < 0.0001). While the correlation between CE-MRI and peak creatine kinase (CK max) was good (r = 0.59, p < 0.001), no correlation was found between the HASTE-TIRM sequence and CK max (r = 0.29, p = ns). CONCLUSIONS: The peri-infarct edema can be depicted with a HASTE-TIRM sequence in addition to the non-viable infarct zone. The HASTE-TIRM sequence shows a higher transmurality of the hyperintense regions than the CE-MRI. The additional area depicted by the HASTE-TIRM sequence could represent functionally impaired but viable myocardium).

Adult↗
PubMed2003

[Establishing a quality management system according to DIN EN ISO 9001:2000 in an academic radiological department].

PURPOSE: Establishing a quality management (QM) system according the guidelines of DIN EN ISO 9001:2000 in an academic radiological department. MATERIALS AND METHODS: To fulfill the requirements of an academic radiological department a quality management system according the guidelines of DIN EN ISO 9001 : 2000 has been established within one year. All important educational, research and patient care issues have been discussed in plenary sessions of all employees of the department twice a week. All core processes of the department have been documented as process instructions and standard operation procedures. RESULTS: Supported by the staff unit "quality assurance" of the university hospital, the QM system has been established during one year. Assisted by all parties of the department, obliging regulations have been established which are well accepted in the daily routine clinical work but also in research and education. The implementation of the QM system caused an additional work load. However, spreading the work load by a consequent responsibility assignment, it could be reduced effectively. CONCLUSION: The implementation of a QM system within the daily routine work of an academic radiological department is feasible. It allows the installation of generally accepted rules which regulate the principal tasks of research and education, and patient care.

Diagnostic Imaging↗
PubMed2003

[Detection of liver lesions with gadolinium-enhanced VIBE sequence in comparison with SPIO-enhanced MRI].

PURPOSE: Detection of malignant liver lesions with gadolinium-enhanced volumetric interpolated breath-hold examination (VIBE) in comparison with SPIO-enhanced MRT (four different SPIO-enhanced T2w sequences) and histological and imaging follow-up in non-cirrhotic livers at 1.5 T. PATIENTS AND METHODS: Twenty-two patients with suspected focal liver lesions prospectively underwent a gadolinium-enhanced 3D VIBE. Four T2w sequences (HASTE sequence, fast spin-echo-sequence with and without fat-saturation, FLASH 2D gradient echo-sequence) after administration of superparamagnetic iron oxide (SPIO) served as gold standard combined with histological work-up in 17 patients and histological and imaging follow-up in five patients. The image quality was evaluated and the detectability of intrahepatic lesions was rated by the alternative free-response receiver operating characteristic (AFROC) analysis. In addition, the contrast-to-noise ratio was compared. RESULTS: Altogether 49 malignant and 35 benign liver lesions were found. Concerning the image quality, VIBE turned out to be of slightly poorer image quality than the SPIO-enhanced examination with HASTE sequence (4.95 vs. 5.0). The fast spin-echo-sequence without fat-saturation demonstrated the highest contrast-to-noise ratio. All sequences showed a comparable certainty in detecting lesion (area under the curve 0.68-0.73) and identifying malignant liver lesions. CONCLUSION: Despite the small number of patients, VIBE seems to be a comparable, inexpensive and fast method in diagnosing malignant liver lesions.

Adult↗
PubMed2002

Overexpression of neuronal Sec1 enhances axonal branching in hippocampal neurons.

The soluble N-ethylmaleimide-sensitive factor-attached protein receptor (SNARE) proteins syntaxin 1 and synaptosomal-associated protein-25 have been implicated in axonal outgrowth. Neuronal Sec1 (nSec1), also called murine unc18a (Munc18a), is a syntaxin 1-binding protein involved in the regulation of SNARE complex formation in synaptic vesicle membrane fusion. Here we analysed whether nSec1/Munc18a is involved in neurite formation. nSec1/Munc18a expressed under the control of an inducible promoter in differentiated PC12 cells as well as in hippocampal neurons appears first in the cell body, and at later times after induction along neurites and in growth cones. It is localised to distinct tubular and punctated structures. In addition, exogenous nSec1/Munc18a inhibited regulated secretion in PC12 cells. Overexpression in PC12 cells of nSec1/Munc18a or its homologue Munc18b, reduced the total length of neurites. This effect was enhanced with nSec1-T574A, a mutant that lacks a cyclin-dependent kinase 5 phosphorylation site and displays an increased binding to syntaxin 1. In contrast, in hippocampal neurons the total length of all primary neurites and branches was increased upon transfection of nSec1/Munc18a. Detailed morphometric analysis revealed that this was a consequence of an increased number of axonal side branches, while the average lengths in primary neurites and of side branches were not affected. From these results we suggest that nSec1/Munc18a is involved in the regulation of SNARE complex-dependent membrane fusion events implicated in the ramification of axonal processes in neurons.

Animals↗
PubMed2001

Temperature quantification using the proton frequency shift technique: In vitro and in vivo validation in an open 0.5 tesla interventional MR scanner during RF ablation.

Open magnetic resonance (MR) scanners allow MR-guided targeting of tumors, as well as temperature monitoring of radio frequency (RF) ablation. The proton frequency shift (PFS) technique, an accurate and fast imaging method for temperature quantification, was used to synthesize thermal maps after RF ablation in an open 0.5 T MR system under ex vivo and in vivo conditions. Calibration experiments with 1.5% agarose gel yielded a chemical shift factor of 0.011 +/- 0.001 ppm/ degrees C (r2 = 0.96). Three gradient echo (GRE) pulse sequences were tested for thermal mapping by comparison with fiberoptic thermometer (Luxtron Model 760) readings. Temperature uncertainty decreased from high to low bandwidths (BW): +/-5.9 degrees C at BW = 15.6 kHz, +/-1.4 degrees C at BW = 3.9 kHz, and +/-0.8 degrees C at BW = 2.5 kHz. In vitro experiments (N = 9) in the paraspinal muscle yielded a chemical shift factor of 0.008 +/- 0.001 ppm/ degrees C. Temperature uncertainty was determined as +/-2.7 degrees C (BW = 3.9 kHz, TE = 19.3 msec). The same experiments carried out in the paraspinal muscle (N = 9) of a fully anesthetized pig resulted in a temperature uncertainty of +/-4.3 degrees C (BW = 3.9 kHz, TE = 19.3 msec), which is higher than it is in vitro conditions (P < 0.15). Quantitative temperature monitoring of RF ablation is feasible in a 0.5 T open-configured MR scanner under ex vivo and in vivo conditions using the PFS technique.

Animals↗
PubMed2001

[MRI in the preoperative diagnosis of chronic sinusitis: comparison with CT].

PURPOSE: To determine the value of MRI in the preoperative evaluation of chronic paranasal sinusitis and to compare the results with CT and intraoperative findings. METHOD/MATERIALS: 42 patients with clinical signs of chronic paranasal sinusitis underwent MRI after CT evaluation on one day, with subsequent functional endoscopic sinus surgery on the next day. Coronary CT was obtained with 5-mm slices and table-feed in the prone position, while MRI was performed in the supine position with coronary T2-TSE + pd and coronary and transverse HASTE, each with 5-mm slice thickness. Aquisition time in MRI was less than 8 minutes. Two radiologists reviewed the CT and MRI scans for signs of sinusitis and detection of anatomical landmarks. The results were correlated with the intraoperative findings. RESULTS: MRI offered no artifacts of dental work and showed more often high quality pictures than CT. CT and MRI demonstrated a good correlation in the detection of mucosal pathologies (kappa = 0.46-0.87) and anatomic variants (kappa = 0.55-0.86). All important anatomical structures could be evaluated sufficiently with MRI for preoperative management. Both diagnostic tools showed an unsatisfactory correlation with intraoperative findings in the ethmoidal complex and maxillary sinus (tau = -0.08-0.3). CONCLUSIONS: MRI is a fast and reliable alternative to preoperative CT in examining paranasal sinuses and offers a good visualization of mucosal changes. CT and MRI both give an unreliable representation of the ethmoidal complex.

Artifacts↗
PubMed2001

[MRI first-pass myocardial perfusion in patients undergoing percutaneous myocardial laser revascularization].

PURPOSE: Evaluation of MRI first-pass myocardial perfusion pre- and post-percutaneous myocardial laser revascularisation (PMR). PATIENTS AND METHODS: MRI was performed in 10 patients with coronary heart disease grade III-IV, 1-4 days prior to PMR, as well as 1-5 days and 6 months after PMR. Contrast enhanced (0.1 ml/kgBw; 4 ml/s) "first-pass" MRI imaging was obtained by breath-hold, ECG-triggered, multislice Turbo-FLASH GRE. For quantitative analysis the absolute and percentual signal-to-noise (S/N)-measurements were calculated. Positron emission tomography (PET) was regarded as the gold standard for myocardial perfusion. RESULTS: The mean values of absolute and % S/N increase revealed no statistical difference between pre- and immediately post-PMR imaging. 6 months following PMR both values were significantly elevated (14.1 vs. 24.4 and 127 vs. 176; p = 0.03 and p = 0.01). However, the non-treated myocardial segments revealed a similar S/N pattern. Intraindividual analysis showed a significant S/N increase post PMR in one patient, and in additional 4 patients 6 months later. PET revealed increased myocardial perfusion in only two patients. Following PMR 5/10 patients experienced a significant reduction of chest pain equivalent to two CCS grades. Two of these had significant S/N elevations but no evidence of increased perfusion by PET. CONCLUSION: S/N first-pass calculations following PMR do not correlate well with the true situation of myocardial perfusion. They seem to be more closely associated with other histological phenomena and possible explanations for the improved clinical symptomatology.

Aged↗
PubMed2001

Proteins induced during adaptation of Acetobacter aceti to high acetate concentrations.

As a typical product of microbial metabolism, the weak acid acetate is well known for its cytotoxic effects. In contrast to most other microbes, the so-called acetic acid bacteria can acquire significant resistance to high acetate concentrations when properly adapted to such hostile conditions. To characterize the molecular events that are associated with this adaptation, we analyzed global protein expression levels during adaptation of Acetobacter aceti by two-dimensional gel electrophoresis. Adaptation was achieved by using serial batch and continuous cultivations with increasing acetate supplementation. Computer-aided analysis revealed a complex proteome response with at least 50 proteins that are specifically induced by adaptation to acetate but not by other stress conditions, such as heat or oxidative or osmotic stress. Of these proteins, 19 were significantly induced in serial batch and continuous cultures and were thus noted as acetate adaptation proteins (Aaps). Here we present first microsequence information on such Aaps from A. aceti. Membrane-associated processes appear to be of major importance for adaptation, because some of the Aap bear N-terminal sequence homology to membrane proteins and 11 of about 40 resolved proteins from membrane protein-enriched fractions are significantly induced.

Acetates↗