Biomedical subjects

Thomas Neumann

Publications and source records attributed to Thomas Neumann.

31 records · Page 2Linked to original sources

PubMed2003

Tandem mass tags: a novel quantification strategy for comparative analysis of complex protein mixtures by MS/MS.

A novel MS/MS-based analysis strategy using isotopomer labels, referred to as "tandem mass tags" (TMTs), for the accurate quantification of peptides and proteins is described. The new tags are designed to ensure that identical peptides labeled with different TMTs exactly comigrate in all separations. The tags require novel methods of quantification analysis using tandem mass spectrometry. The new tags and analysis methods allow peptides from different samples to be identified by their relative abundance with greater ease and accuracy than other methods. The new TMTs permit simultaneous determination of both the identity and relative abundances of peptide pairs using a collision induced dissociation (CID)-based analysis method. Relative abundance measurements made in the MS/MS mode using the new tags are accurate and sensitive. Compared to MS-mode measurements, a very high signal-to-noise ratio is achieved with MS/MS based detection. The new tags should be applicable to a wide variety of peptide isolation methods.

Isotopes↗

PubMed2003

Pulmonary vein diameter reduction after radiofrequency catheter ablation for paroxysmal atrial fibrillation evaluated by contrast-enhanced three-dimensional magnetic resonance imaging.

BACKGROUND: Radiofrequency catheter ablation (RFCA) is a promising intervention to treat atrial fibrillation. However, pulmonary vein (PV) stenosis after RFCA has been reported. The aim of this study was to investigate the incidence and time course of pulmonary vein stenosis after RFCA within a period of 3 months. Contrast-enhanced magnetic resonance angiography (MRA) was used to visualize pulmonary veins and was compared with radiographic angiography. METHODS AND RESULTS: Forty-six consecutive patients with symptomatic paroxysmal atrial fibrillation had RFCA in the orifice of 138 pulmonary veins. Comparison of diameters measured in 44 untreated vessels either by radiographic angiography or with MRA established the reliability of MRA (r=0.934). MRA measurements revealed an incidence of relevant diameter reductions of > or =25% or stenosis of > or =50% after RFCA of 25 of 138 (18.1%) treated vessels 1 day and/or 3 months after ablation. A progression of diameter reduction after RFCA was observed in 8.3% (maximum 75%), whereas a regression was observed in 6.3% of treated PVs. Ablation at a radial angle of >180 degrees of a pulmonary vein orifice increased the risk of diameter reduction significantly compared with ablation at a radial angle < or =180 degrees (P=0.002). CONCLUSIONS: The occurrence and progression of PV stenosis is a potential significant complication of RFCA in the orifice of pulmonary veins. These findings may have an impact on the technical performance of this intervention. In addition, long-term studies will be necessary to evaluate lumen reduction over time. MRA is a noninvasive, reproducible imaging modality for this purpose.

Angiography↗

PubMed2003

Chromosomal alterations in osteosarcoma cell lines revealed by comparative genomic hybridization and multicolor karyotyping.

We characterized the chromosomal alterations in eight osteosarcoma cell lines (OST, HOS, U-2 OS, ZK-58, MG-63, SJSA-1, Saos-2, and MNNG) by comparative genomic hybridization (CGH); gains and losses of DNA sequences were defined as chromosomal regions with a fluorescence ratio, wherein all of the 95% confidence interval was above 1.25 and below 0.75, respectively. In four of 8 cell lines, multicolor karyotyping (MK) was added. CGH revealed the average number of aberrations per cell line was 20.8 (range: 10-31); the average numbers of gains and losses were 11.1 and 9.6, respectively. The frequent gains were identified on 1p21 approximately q24, 1q25-q31, 7p21, 7q31, 8q23 approximately q24, and 14q21; frequent losses were at 18q21 approximately q22, 18q12, 19p, and 3p12 approximately p14. High-level gains were observed on 8q23 approximately q24, 5p, and 1p21 approximately p22. MK revealed the most common translocations in the four cell lines were t(8;9), t(1;3), t(3;5), t(1;13), t(2;6), t(3; 17), t(1;15), t(10;20), and t(6;20). Chromosomes 1, 3, 8, 9, and 20 were most frequently involved in translocation events. The concordance rate of aberrations in CGH and translocations in MK was 76%. MK was useful to identify the chromosomal alterations and as a supplement to the CGH results in three of four chromosomes.

Bone Neoplasms↗

PubMed2003

Tissue engineering of perfused microvessels.

One major obstacle toward the creation and survival of larger, three-dimensional tissues is the lack of a vascular network that provides transport of oxygen, nutrients, and metabolic byproducts. Although attempts to create microvasculature in vitro have been described previously (Microcirculation 2 (1995), 377; Tissue Eng. 6 (2000), 105; Ann. NY Accd. Sci. 944 (2001), 443), these methods depend on vascularization of void spaces within the tissue-construct or on the utilization of empty capillary networks by host vessels. In the present study, we examined the possibility of creating perfused microvessels in vitro that can be included in an artificial tissue. First, strands of nylon line with their ends fit into microtubing were positioned within small perfusion chambers. Vascular smooth muscle cells (SMCs) were then seeded onto the nylon strands and tubing. The cells multiplied to form concentric layers. Layer thickness was approximately 100 microm after 21 days and 150 microm after 28 days of culture. The lines were then extracted and the chambers connected to a perfusion system. The vessels were continuously perfused with culture medium over 7 days without failure. Artificial microvessels may prove useful in tissue engineering and as models for vascular research.

Animals↗

PubMed2003

Microwave, irrigated, pulsed, or conventional radiofrequency energy source: which energy source for which catheter ablation?

The aim of the study was to compare the diameter of endomyocardial lesions induced with the delivery of microwave, cooled, or pulsed energy versus conventional RF energy. In vitro tests were performed in fresh endomyocardial preparations of pig hearts in a 10-L bath of NaCl 0.9% solution at 37 degrees C and constant 1.5 L/min flow. Ablation 7 Fr catheters with 4-mm tip electrodes were used, except for the delivery of microwave energy. Energy delivery time was set to 60 s/50 W in all experiments. Cooled energy delivery was performed with a closed irrigation catheter. Pulsed energy delivery was performed using a special controller with a duty-cycle of 5 ms. Microwave energy was delivered with a 2.5-GHz generator and 10-mm antenna. Electrode temperature and impedance were measured simultaneously. After ablation, lesion length, width, and depth were measured with microcalipers, and volume calculated by a formula for ellipsoid bodies. Each energy delivery mode was tested in ten experiments. The deepest lesions were created with cooled energy delivery, and the largest volume by microwave energy delivery. Pulsed RF produced significantly deeper lesions than conventional RF energy delivery. Cooled or pulsed RF energy delivery created deeper transmural lesions than conventional RF. To create linear lesions at anatomically complex sites (isthmus), microwave energy seemed superior by rapidly creating deep and long lesions.

Animals↗

PubMed2003

Quality-of-life in patients with paroxysmal atrial fibrillation after catheter ablation: results of long-term follow-up.

Paroxysmal atrial fibrillation (PAF) significantly impairs patients' quality-of-life (QOL). The effect on QOL of recently developed ablation techniques with curative intention has not been studied. Thirty patients (21 men, age 54.1 +/- 9.5 years) with PAF (duration 5.6 +/- 5.2 years) who failed antiarrhythmic (3.8 +/- 1.2 trials) drug therapy underwent catheter ablation. The follow-up time was 33.9 +/- 11 months. QOL was assessed preablation, 3, 6, 9, 12, 24, and 36 months after catheter ablation. The Medical Outcomes Survey Short-Form (SF-36), scored on a 0-100 scale for each of eight domains: bodily pain, general health, mental health, physical functioning, role-emotional, role-physical, social functioning, and vitality, was used. Simultaneously, patients filled out a symptom-specific checklist (SSC) with seven clinical items scored 1-4 (1 best): dyspnea, nausea, palpitations, anxiety, syncope, presyncope, and NYHA classification. Patients with successful catheter ablation had a significant benefit in seven of eight subscales while patients with recurrence had an impact on QOL in two of eight subscales. Using SSC, a successful ablation influenced scores in all seven items while patients with recurrence had a significant change of clinical symptoms in only one item, anxiety. The subscales of the study group compared to a healthy population show higher scores after 24 months of follow-up. Patients with PAF experience a significant improvement in QOL after a successful catheter ablation. In contrast, in patients with recurrence of PAF the QOL showed improvement to a lesser extent and patients experienced ongoing symptoms.

Atrial Fibrillation↗

PubMed2003

Multicolor karyotyping in acute myeloid leukemia.

Cytogenetic data have significantly contributed to our understanding of the heterogeneity of acute myeloid leukemia (AML). In AML, numerous recurrent chromosomal aberrations have been identified, and several of them, e.g. t(8;21)(q22;q22), t(15;17)(q22;q11-12), inv(16)(p13q22), are specific for distinct subgroups. Furthermore, chromosomal aberrations have proved to be of paramount prognostic importance for remission induction and survival. Chromosome analysis using classical cytogenetic banding techniques often fails to completely resolve complex karyotypes and cryptic translocations not identifiable by these techniques have been detected using molecular cytogenetic methods. While fluorescence in situ hybridization (FISH) has become an indispensable tool for screening and follow-up of known aberrations, the techniques of spectral karyotyping (SKY) and multiplex-fluorescence in situ hybridization (M-FISH) allow for the simultaneous visualization of all chromosomes of a metaphase in a single hybridization step, and thereby enable screening for the aberrations present without their prior knowledge. Therefore, with the introduction of these techniques in 1996 the comprehensive analysis of complex karyotypes and the identification of new, hitherto cryptic translocations and, ultimately, the identification of new disease subgroups seemed possible. Since, more than 600 cases of AML and MDS have been analyzed. Herein, we attempt to summarize the data published and discuss what has been achieved towards realization of these goals.

Acute Disease↗

PubMed2003

Tissue engineering of skeletal muscle using polymer fiber arrays.

The purpose of this study was to assess a new scaffold design for muscle tissue engineering: arrays of parallel-oriented polymer microfibers. First, C2C12 skeletal myoblasts were seeded onto single, laminin-coated polypropylene fibers and their growth and alignment were characterized. With the aim of creating skeletal muscle sheets, it was then investigated whether cell layers of single fibers merged when in close proximity to neighboring fibers. The optimal fiber spacing needed to achieve cell alignment with the lowest possible content of scaffold material was established. Further, it was assessed whether such a cell sheet became contractile and whether it survived in vitro for extended periods of time. C2C12 cells, cultured on fibers 10 to 15 microm in diameter, formed up to 50-microm-thick layers of longitudinally aligned cells. Four different groups based on fiber spacing (30 to 35, 50 to 55, 70 to 75, and 90 to 95 microm) were evaluated. Complete cell sheets formed between fibers that were spaced 55 microm apart or less; larger spacing led to no or incomplete sheets. C2C12 cells, seeded onto a 10 x 20 mm fiber array, formed a contractile cell sheet that was maintained in vitro for 70 days. Larger, three-dimensional structures might be created by arranging fibers in several layers or by stacking cellular sheets.

Animals↗

PubMed2003

MR Imaging in Wegener granulomatosis of the spinal cord.

Wegener granulomatosis is a multisystemic disorder characterized by necrotizing vasculitis that primarily involves the respiratory tract. The orbits, heart, skin, joints, and nervous system are frequently involved. We describe the MR imaging findings of Wegener granulomatosis in the cervical spine and correlate them with the histopathologic features. MR imaging showed epidural liquid masses surrounded by granulomatous masses that compressed the cervical myelin from behind.

Cervical Vertebrae↗

PubMed2002

Novel der(1)t(1;19) in two patients with myeloid neoplasias.

Cytogenetic studies can be useful in the clinical management of patients with leukemia. They may also give a clue to leukemogenesis and/or pathogenesis. Numerous disease-specific chromosomal aberrations have been and continue to be identified. Translocation (1;19)(q21 through q23;p13.3) involving the long arm of chromosome 1 and the short arm of chromosome 19 is usually associated with acute lymphoblastic leukemia. We found a new translocation involving one virtually identical breakpoint 19p13 and one distinct 1p13 in two cases of myeloid neoplasms. Studies of bone marrow and peripheral blood specimens specified in one of our patients acute myeloid leukemia and in an other myelodysplastic syndrome. Conventional cytogenetics was supplemented by spectral karyotyping (SKY), microdissection, and fluorescence in situ hybridization. Our first case showed a der(1)t(1;19)(p13;p13.1) as the sole chromosomal change. In addition to this translocation, a pericentric inversion within chromosome 10 and with a cryptic t(10;11) were detected by SKY in the second case. Translocation (1;19)(p13;p13.1) may play a role in the leukemogenesis of myeloid diseases.

Adult↗

PubMed2002

Transcatheter closure of atrial septal defect and patent foramen ovale in adult patients using the Amplatzer occlusion device: no evidence for thrombus deposition with antiplatelet agents.

Transcatheter closure of atrial septal defect (ASD) and patent foramen ovale (PFO) using the Amplatzer septal occluder (AGA Medical, Minneapolis, Minn) is an alternative to surgical closure. There are only limited data on the thrombogenic potential of the device. Thirty-seven patients (14 men, 23 women) underwent device closure of their ASD (n = 21) or PFO (n = 16) at a mean age of 47 +/- 14 years (range, 18-72). The device was successfully deployed in all patients. Thirty-three of 37 patients received antiplatelet therapy with clopidogrel bisulfate and aspirin for a total of 6 months. Four patients in atrial fibrillation were also anticoagulated (international normalized ratio 2.0 to 3.0). No thrombus was detected in any patient on either side of the device by transthoracic and transesophageal echocardiography and there were no cases of symptomatic thromboembolism. Right-to-left interatrial shunting was diagnosed by contrast transesophageal echocardiography with the Valsalva's maneuver. At 1-month follow-up, minimal right-to-left shunting was detected in 6 patients (2 PFO, 4 ASD). Two patients (PFO) had minimal shunting at 1 month but not at 6 months. In 3 patients (ASD), inducible right-to-left shunting persisted at 6 months. In conclusion, our results obtained from a modest number of patients indicate that antiplatelet therapy is safe and effective in preventing thrombus formation on the septal occluder surface.

Adolescent↗

PubMed2002

Proteomics and the Proteome - IBC's Fifth Annual Conference. 18-20 February, Geneva, Switzerland.

The complexity of humans lies in their proteins, not genes. Although a number of technologies are currently employed to analyze protein complexity, no single proteomics technology is adequate. Varying concentrations and wide dynamic range are among the major challenges in protein analyses. On average, each protein has the ability to exist in more than five different forms in a cell, thus, novel concepts in target discovery that are compliant with this 'isoform world' require development.

Journal Article↗

PubMedDate not supplied

Isolation of N-terminal protein sequence tags from cyanogen bromide cleaved proteins as a novel approach to investigate hydrophobic proteins.

A novel method for the isolation of protein sequence tags to identify proteins in a complex mixture of hydrophobic proteins is described. The PST (Protein Sequence Tag) technology deals with the isolation and MS/MS based identification of one N-terminal peptide from each polypeptide fragment generated by cyanogen bromide cleavage of a mixture of proteins. PST sampling takes place after sub-cellular fractionation of a complex protein mixture to give enrichment of mitochondrial proteins. The method presented here combines effective sample preparation with a novel peptide isolation protocol involving chemical and enzymatic cleavage of proteins coupled to chemical labeling and selective capture procedures. The overall process has been very successful for the analysis of complex mixtures of hydrophobic proteins, particularly membrane proteins. This method substantially reduces the complexity of a protein digest by "sampling" the peptides present in the digest. The sampled digest is amenable to analysis by liquid chromatography tandem mass spectrometry (LC-MS/MS). Methods of "sampling" protein digests have great value' if they can provide sufficient information to identify substantially all of the proteins in the sample while reducing the complexity of the sample to maximize the efficient usage of LC-MS/MS capacity. The validity of the process is demonstrated for mitochondrial samples from S. cerevisiae. The proteins identified by the PST technology are compared to the proteins identified by the conventional technology 2-D gel electrophoresis as a control.

Amino Acid Sequence↗