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S Weber

Publications and source records attributed to S Weber.

At least 37 records · Page 2Linked to original sources
PubMed2004

A linear programming approach to limited angle 3D reconstruction from DSA projections.

OBJECTIVES: We investigate the feasibility of binary-valued 3D tomographic reconstruction using only a small number of projections acquired over a limited range of angles. METHODS: Regularization of this strongly ill-posed problem is achieved by (i) confining the reconstruction to binary vessel/non-vessel decisions, and (ii) by minimizing a global functional involving a smoothness prior. RESULTS: Our approach successfully reconstructs volumetric vessel structures from three projections taken within 90 degrees. The percentage of reconstructed voxels differing from ground truth is below 1%. CONCLUSION: We demonstrate that for particular applications--like Digital Subtraction Angiography--3D reconstructions are possible where conventional methods must fail, due to a severely limited imaging geometry. This could play an important role for dose reduction and 3D reconstruction using non-conventional technical setups.

Angiography, Digital Subtraction↗
PubMed2004

Efficiency of nanofiltration for the elimination of steroids from water.

Steroid hormones such as the synthetic 17-alpha-ethinylestradiol often persist in the sewage treatment process and metabolites of the natural steroids like estrone from estradiol accumulate resulting in relevant amounts in the aquatic environment. Since biological removal of steroids in the sewage treatment plant is not successfully complete, physical processes such as membrane filtration may become more important. We investigated the elimination of natural and synthetic steroids by nanofiltration using a laboratory membrane reactor. Chemical analysis of 17-beta-estradiol, estrone, estriol, 17-alpha-ethinylestradiol, mestranol, diethylstilbestrol, progesterone and beta-sitosterine was performed after solid phase extraction by GC-MS with standard addition. The elimination rate depended on the nanofiltration membrane material. LFC1 membrane consisting of polyamide removed the steroids over 99% whereas PES10 membrane consisting of hydrolysed polyethersulfone was less efficient, obviously caused by different pore sizes and permeability of the membrane structure.

Animals↗
PubMed2003

Hippocampal volume and cell proliferation after acute and chronic clozapine or haloperidol treatment.

The dentate gyrus contains progenitor cells possessing the capacity to proliferate until and throughout adulthood. There is little information about the influence of antipsychotics on cell proliferation. To address this, we investigated the influence of acute and chronic haloperidol and clozapine treatment on the total number of newly dividing cells and hippocampal volume using an animal model with doses equivalent to the therapeutic range in humans. Rats were treated with either acute or 28 days haloperidol (1 mg/kg i.p. or 1,5 mg/kg/day oral) or clozapine (30 mg/kg i.p. or 45 mg/kg/day oral). After BrdU injection, immunohistochemistry was performed in serial hippocampal brain sections. Total BrdU-labeled cell number and hippocampus volume were estimated using stereological methods. Neither neuroleptic altered total number of newly dividing cells in the dentate gyrus. In contrast, chronic haloperidol treatment did increase total hippocampal volume suggesting that haloperidol alters neuroplastic processes or glial morphology rather than cell proliferation.

Animals↗
PubMed2003

Enhanced spatiotemporal laser-beam smoothing in gas-jet plasmas.

Spatiotemporal smoothing of large-scale laser intensity fluctuations is observed for a laser beam focused into underdense helium plasmas. This smoothing is found to be severely enhanced when focusing the laser beam into a helium gas jet. In contrast to other experiments with preformed plasmas, the average and the peak laser intensities are well below the threshold for ponderomotive self-focusing. The coherence characteristics of the transmitted light are measured for various electron densities, and the smoothing effect is explained by multiple scattering of laser light on self-induced density perturbations.

Journal Article↗
PubMed2003

N-terminal pro-brain natriuretic peptide as a diagnostic marker of early pulmonary artery hypertension in patients with systemic sclerosis and effects of calcium-channel blockers.

OBJECTIVE: To evaluate N-terminal pro-brain natriuretic peptide (NT-proBNP) as a marker of early pulmonary artery hypertension (PAH) and to study changes in the levels of this marker following treatment with dihydropyridine-type calcium-channel blocker (DTCCB) in patients with systemic sclerosis (SSc). METHODS: We evaluated 40 consecutive SSc patients who had been hospitalized for followup care (mean +/- SD age 56 +/- 11 years and mean +/- SD duration of cutaneous disease 9 +/- 9 years; 27 with limited cutaneous and 13 with diffuse cutaneous disease) but who had no clinical symptoms of heart failure and had a normal left ventricular ejection fraction. At baseline, 10 patients had PAH, defined as a systolic pulmonary artery pressure (sPAP) >40 mm Hg, as measured by echocardiography. Levels of NT-proBNP were determined at baseline (after discontinuation of DTCCB treatment for 72 hours), after taking 3 doses of DTCCB following treatment reinitiation (assessment 1), and after 6-9 months of continuous DTCCB treatment (assessment 2) in the 20 patients who attended regular appointments (including the 10 patients with PAH at baseline). RESULTS: At baseline, 13 patients had high NT-proBNP values for their ages. High NT-proBNP levels identified patients with PAH with a sensitivity of 90%, a specificity of 90.3%, a positive predictive value of 69.2%, and a negative predictive value of 96%. The NT-proBNP level correlated with the sPAP (r = 0.44; P = 0.006). By assessment 1, the number of patients with PAH and high levels of NT-proBNP had decreased from 9 of 10 to 2 of 10 (P = 0.02). This decrease was partially sustained at assessment 2 (4 of 10 patients; P = 0.06). CONCLUSION: NT-proBNP is a useful biologic marker that can be used to diagnose early PAH in SSc patients without clinical heart failure. Measurement of NT-proBNP may be valuable for the evaluation of treatment with DTCCB and vasodilators in patients with PAH.

Aged↗
PubMed2003

Amount of co-transplanted donor-derived leukocytes determines in-vivo microchimerism and mixed lymphocyte culture changes post-liver transplantation.

OBJECTIVE: To evaluate the impact of passenger leukocytes in liver grafts on the rate of microchimerism induction after liver transplantation and to evaluate immunological changes thereafter based on serial donor-specific MLC's in these patients. METHODS: 26 orthotopic liver transplant recipients were prospectively evaluated for immunological changes based on the co-transplantation of donor-derived leukocytes. Intraoperatively harvested liver biopsies and peripheral blood-lymphocytes of liver transplant recipients were sampled at various time points. Donor spleen cells were obtained during organ procurement. RESULTS: HLA-PCR analysis demonstrated a stable pattern of microchimerism in 15 out of 26 patients. Microchimerism was detectable by PCR up to a mean of 7 weeks after transplantation, when chimerism in the peripheral blood became negative. Passenger donor leukocytes were present in all biopsies obtained during backtable preparation of the liver graft. For the 15 patients presenting microchimerism the rate of passenger leukocytes in the liver graft biopsies showed a mean of 155.8 leukocytes per mm 2 liver tissue (SD +/- 23.2 cells/mm2, range 121 to 217 cells per mm2 tissue). Otherwise patients without chimerism showed a mean of 90.4 passenger leukocytes per mm2 tissue (SD +/- 14.5 cells/mm2, range: 52 to 99 cells/mm2). Lymphocyte proliferation, determined by donor-specific "multiple" single-way- mixed-lymphocyte-cultures (dsmMLC) was reduced to a mean of 62.2 % of preoperative values (SD +/- 14.5 %, range 33 % to 88 %) in the 15 patients with stable microchimerism. Otherwise in the 11 patients without microchimerism dsmMLC results stayed at continuously higher levels with a mean of 106 % (SD +/- 13.4, range 92 % to 134 %). CONCLUSIONS: The results from these studies of microchimerism and lymphocyte reactivity after liver transplantation suggest that the co-transplantation of donor leukocytes plays an important and active role in the modulation of the host-immune system.

Biopsy, Needle↗
PubMed2003

The role of staging laparoscopy in hepatobiliary malignancy: prospective analysis of 401 cases.

BACKGROUND: Patients with potentially resectable hepatobiliary malignancy are frequently found to have unresectable tumors at laparotomy. We prospectively evaluated staging laparoscopy in patients with resectable disease on preoperative imaging. METHODS: Staging laparoscopy was performed on 410 patients with potentially resectable hepatobiliary malignancy. The preoperative likelihood of resectability was recorded. Data on preoperative imaging, operative findings, and hospital course were analyzed. RESULTS: Laparoscopic inspection was complete in 291 (73%) patients. In total, 153 patients (38%) had unresectable disease, 84 of whom were identified laparoscopically, increasing resectability from 62% to 78%. On multivariate analysis, a complete examination, preoperative likelihood of resection, and primary diagnosis were significant predictors of identifying unresectable disease at laparoscopy. The highest yield was for biliary cancers, and the lowest was for metastatic colorectal cancer. In patients with unresectable disease identified at laparoscopy, the mean hospital stay was 3 days, and postoperative morbidity was 9%, compared with 8 days and 27%, respectively, in patients found to have unresectable disease at laparotomy. CONCLUSIONS: Laparoscopy spared one in five patients a laparotomy while reducing hospital stay and morbidity. Targeting laparoscopy to patients at high risk for unresectable disease requires consideration of disease-specific factors; however, the surgeons' preoperative impression of resectability is also important.

Aged↗
PubMed2003

A regional outbreak of S. Enteritidis phage type 5, traced back to the flocks of an egg producer, Austria.

In the spring and summer of 2002, the Nationale Referenzzentrale für Salmonellen (National Reference Centre for Salmonella - NRCS) in Austria noticed a cluster of human Salmonella enterica subsp. enterica ser. Enteritidis phage type 5 (S. Enteritidis PT5) infections in two neighbouring districts of Austria. Another small outbreak of S. Enteritidis PT5 infections that occurred in the same region in 1999 had been traced back to the flocks of a local egg producer (approximately 6 000 hens). Attention was therefore again directed at this farm. The results of voluntary bacteriological examinations from the farm and further epidemiological investigations identified the same egg producer as the source of the second outbreak. The 70 human isolates of S. Enteritidis PT5 ascertained in 2002 represented a minority of all infections. It is realistic to estimate that several hundred infections occurred in the course of the 2002 outbreak. The farmer had not vaccinated new flocks against Salmonella since August 2001. It is likely that the change in vaccination policy resulted in the reappearance of the S. Enteritidis PT5 infections. By the end of September 2002 the farmer had stopped selling untreated table eggs. In October 2002 only one isolate of S. Enteritidis PT5 was ascertained in the region.

Adult↗
PubMed2002

Improved Agrobacterium-mediated transformation of sunflower (Helianthus annuus L.): assessment of macerating enzymes and sonication.

Agrobacterium -mediated transformation of shoot apices of sunflower (Helianthus annuus L.) was evaluated following wounding by cell-wall-digesting enzymes and sonication. The frequency of explants with regenerated shoots expressing GUS (beta-glucuronidase) or GFP (green fluorescent protein) increased following treatment with the macerating enzymes cellulase Onozuka R-10 and pectinase Boerozym M5, whereas treatment with macerozyme R-10 had a negative effect. When a combination of cellulase (0.1%) and pectinase (0.05%) was used, the rate of explants with uniformly GUS-positive shoots increased at least twofold. The transient expression of reporter genes was also enhanced using sonication (50 MHz; 2, 4 and 6 s), but stable expression in regenerated shoots following 4 weeks of selection did not increase with this treatment. Enzyme treatment alone (0.1% cellulase and 0.05% pectinase) was superior to a combined treatment of sonication and enzymes with respect to stable transformation. Polymerase chain reaction analyses of shoots recovered by grafting from transformation experiments using GFP as the reporter gene demonstrated the stable integration of the transgene. Regenerated plants were fertile and seeds could be harvested.

Cellulase↗
PubMed2002

Immunization by particle-mediated transfer of the granulocyte-macrophage colony-stimulating factor gene into autologous tumor cells in melanoma or sarcoma patients: report of a phase I/IB study.

The primary objective of this phase I study was to determine the safety of an autologous tumor vaccine given by intradermal injection of lethally irradiated granulocyte-macrophage colony-stimulating factor (GM-CSF) gene-transfected autologous melanoma and sarcoma cells. Secondary objectives included validation of the gene delivery technology (particle-mediated gene transfer), determining the host immune response to the tumor after vaccination, and monitoring patients for evidence of antitumor response. Sixteen patients were treated with either of two different doses of GM-CSF-treated tumor cells. One patient received treatment with both doses of tumor cells. No treatment-related local or systemic toxicity was noted in any patient. Patients administered 100% treated cells (i.e., with a preparation of tumor cells that had all been exposed to GM-CSF DNA transfection) had a more extensive lymphocytic infiltrate at the vaccine site than did patients given 10% treated cells (a preparation of tumor cells in which 10% had been exposed to GM-CSF transfection) or nontreated tumor. The generation of a systemic immune response to autologous tumor by a delayed-type hypersensitivity response to the intradermal placement of nontransfected tumor cells was noted in one patient. One patient had a transient partial response of metastatic tumor sites. The entire procedure, from tumor removal to vaccine placement, was accomplished in less than 6 hr in all patients. Four of 17 patient tumor preparations produced greater than 3.0 ng of GM-CSF per 10(6) cells per 24 hr in vitro. The one patient with greater than 30 ng of GM-CSF per 10(6) cells per 24 hr in vitro had positive DTH, a significant histologic inflammatory response, and clinically stable disease. This technique of gene transfer was safe and feasible, but resulted in clinically relevant levels of gene expression in only a minority of patients.

Biolistics↗
PubMed2002

Diffusion studies in non-oxide ceramics: analytical aspects of the use of ion implanted stable tracers and SIMS.

The physical and chemical properties of complex non-oxide ceramic materials require advanced methods of diffusivity determination. In this study, we present a method based on the high-dose ion implantation of stable tracers in combination with secondary ion mass spectroscopy for depth profiling. The analytical basics, advantages and problems of the method are discussed for two examples of complex materials, the Si-B-C-N precursor ceramics and the Ti-based transition metal diborides. We demonstrate that is possible to measure the temperature dependence of diffusivities, especially for ceramic systems with low diffusivities, for systems that contain elements for which no suitable radioactive tracers exist for extended measurements.

Ceramics↗
PubMed2002

Pallidal deep brain stimulation in patients with cervical dystonia and severe cervical dyskinesias with cervical myelopathy.

OBJECTIVES: Surgical treatment of complex cervical dystonia and of cervical dyskinesias associated with cervical myelopathy is challenging. In this prospective study, the long term effect of chronic pallidal stimulation in cervical dystonia and on combining the technique with spinal surgery in patients with severe cervical dyskinesias and secondary cervical myelopathy is described. METHODS: Eight patients with a history of chronic dystonia who did not achieve adequate benefit from medical treatment or botulinum toxin injection participated in the study. Five patients had complex cervical dystonia with tonic postures and phasic movements. Three patients had rapidly progressive cervical myelopathy secondary to severe cervical dyskinesias and dystonia in the context of a generalised movement disorder. Quadripolar electrodes were implanted in the posteroventral lateral globus pallidus internus with stereotactic CT and microelectrode guidance. In the three patients with secondary cervical myelopathy, spinal surgery was performed within a few weeks and included multilevel laminectomies and a four level cervical corporectomy with spinal stabilisation. RESULTS: Improvement of the movement disorder was noted early after pallidal surgery, but the full benefit could be appreciated only with a delay of several months during chronic stimulation. Three months after surgery, patients with cervical dystonia had improved by 38% in the severity score, by 54% in the disability score, and by 38% in the pain score of a modified version of the Toronto western spasmodic torticollis rating scale. At a mean follow up of 20 months, the severity score had improved by 63%, the disability score by 69%, and the pain score by 50% compared with preoperatively. There was also sustained amelioration of cervical dyskinesias in the three patients who underwent spinal surgery. Lead fractures occurred in two patients. The mean amplitude needed for chronic deep brain stimulation was 3.8 V at a mean pulse width of 210 micros, which is higher than that used for pallidal stimulation in Parkinson's disease. CONCLUSIONS: Chronic pallidal stimulation is effective for complex cervical dystonia and it is a useful adjunct in patients with cervical dyskinesias and secondary cervical myelopathy who undergo spinal surgery.

Adult↗
PubMed2002

Feasibility and validity of transcranial duplex sonography in patients with acute stroke.

OBJECTIVES: To evaluate in a prospective multicentre setting the feasibility of transcranial colour coded duplex sonography (TCCS) for examination of the middle cerebral artery (MCA) in patients with acute hemispheric stroke, and to assess the validity of sonographic findings in a subgroup of patients who also had a correlative angiographic examination. METHODS: TCCS was performed in 58 consecutive patients within six hours of the onset of a moderate to severe hemispheric stroke. Ultrasound contrast agent (Levovist) was applied if necessary. Thirty two patients also had computed tomography angiography (n=13), magnetic resonance angiography (n=18), or digital subtraction angiography (n=1). In 14 of these patients, both the sonographic and corresponding angiographic examination were performed within six hours of stroke onset (mean time difference between TCCS and angiography 0.8 hours). Eighteen patients, in whom angiography was carried out more than 24 hours after stroke onset, had a follow up TCCS for method comparison (mean time difference 6.1 hours). RESULTS: Initial unenhanced TCCS performed 3.4 (SD 1.2) hours after the onset of symptoms depicted the symptomatic MCA mainstem in 32 patients (55%) (13 occlusions, one stenosis, 18 patent arteries). After signal enhancement, MCA status could be determined in 54 patients (93%) (p<0.05), showing an occlusion in 25, a stenosis in two, and a patent artery in 27 patients. In 31 of the 32 patients who had correlative angiography, TCCS and angiography produced the same diagnosis of the symptomatic MCA (10 occlusions, three stenoses, 18 patent arteries); TCCS was inconclusive in the remaining one. CONCLUSION: TCCS is a feasible, fast, and valid non-invasive bedside method for evaluating the MCA in an acute stroke setting, particularly when contrast enhancement is applied. It may be a valuable and cost effective alternative to computed tomography and magnetic resonance angiography in future stroke trials.

Acute Disease↗
PubMed2002

Effect of chronic pallidal deep brain stimulation on off period dystonia and sensory symptoms in advanced Parkinson's disease.

OBJECTIVE: To investigate the efficacy of chronic pallidal deep brain stimulation (DBS) on off period dystonia, cramps, and sensory symptoms in advanced Parkinson's disease (PD). METHODS: 16 patients (6 women, 10 men; mean age at surgery 65 years) suffering from advanced PD were followed up prospectively for one year after implantation of a monopolar electrode in the posteroventral lateral globus pallidus internus. Unilateral DBS was performed in 9 patients. 10 patients had bilateral procedures (contemporaneous bilateral surgery in 7 and staged bilateral surgery in 3 instances). The decision whether to perform unilateral or bilateral surgery depended on the clinical presentation of the patient. Patients were formally assessed preoperatively, at 3-5 days, 3 months, and 12 months after surgery. RESULTS: In patients who underwent unilateral surgery, pain was present in 7 (78%), off dystonia in 5 (56%), cramps in 6 (67%), and dysaesthesia in 4 (44%). In patients who underwent bilateral surgery, pain was present in 7 (70%), off dystonia in 6 (60%), cramps in 7 (70%), and dysaesthesia in 4 (40%). With unilateral DBS, contralateral off period dystonia was improved by 100% at 1 year postoperatively, pain by 74%, cramps by 88%, and dysaesthesia by 100%. There was less pronounced amelioration of ipsilateral off period dystonia and sensory symptoms. With bilateral DBS, total scores for dystonia were improved by 86%, for pain by 90%, for cramps by 90%, and for dysaesthesia by 88%. The benefit appeared early at the first evaluation 3-5 days after surgery and was stable throughout the follow up period. CONCLUSIONS: Pallidal DBS yields major improvement of off period dystonia, cramps, and sensory symptoms in patients with advanced PD.

Adult↗
PubMed2001

Immunization with gp96 from Listeria monocytogenes-infected mice is due to N-formylated listerial peptides.

N-Formylated (N-f-met) peptides derived from proteins of the intracellular bacterium Listeria monocytogenes generate a protective, H2-M3-restricted CD8 T cell response in C57BL/6 mice. N-f-met peptide-specific CTL were generated in vitro when mice previously immunized with gp96 isolated from donor mice infected with L. monocytogenes were stimulated with these peptides. No significant peptide-specific CTL activity was observed in mice immunized with gp96 from uninfected animals. Masses corresponding to one N-f-met peptide were found by matrix-assisted laser desorption/ionization-mass spectrometry on gp96 isolated from C57BL/6 mice infected with L. monocytogenes, but not on gp96 from noninfected mice. Therefore, bacterial N-f-met peptides from intracellular bacteria can bind to gp96 in the infected host, and gp96 loaded with these peptides can generate N-f-met-peptide-specific CTL. We assume a unique role of gp96 in Ag processing through the H2-M3 pathway.

Animals↗