PubMed Health⌕ Search

Biomedical subjects

R Müller

Publications and source records attributed to R Müller.

At least 91 records · Page 5Linked to original sources
PubMed2001

Radiotherapy of esthesioneuroblastoma.

PURPOSE: Only 3% of all malignant intranasal tumors are esthesioneuroblastomas (ENB). As the tumor is very rare, the number of ENB treated in individual departments is small. In order to evaluate the efficacy of radiotherapy (RT), patients' data of 2 centres were analysed with reference to new reports in literature. METHODS AND MATERIALS: From 1981 to 1998, 17 patients with ENB, 8 men and 9 women aged between 6 and 81 years, were treated in the departments of radiotherapy of the universities of Cologne and Muenster. The tumors were Kadish Stage B in 4/17 patients and Stage C in 13/17 patients. Treatment included incomplete surgery and irradiation in 2/17 patients, adjuvant RT postoperatively in 6/17 patients, definitive RT in 7/17 patients and RT after incomplete surgery of recurrent tumors in 2/17 patients. Postoperatively, the median target dose of EBRT was 56 (range 50-60) Gy; for definitive RT it was 58 (range 40-70) Gy. RESULTS: After a median follow-up period of 86 (range 2-208) months 10/17 patients showed no evidence of disease (NED). There were 6 patients treated with radical complete surgery plus postoperative irradiation and 5 of them were NED. There were 7 patients treated with only irradiation and 3 of those patients were NED. Of 2 patients with incomplete surgery and irradiation there was one patient NED. Of 2 patients with incomplete resection of recurrent tumor who received irradiation, there was one patient NED. 2 of the patients with NED died after 22 and 94 months respectively. 4/17 patients died as a result of local recurrence and 2/17 patients as a result of distant metastases (liver, brain). One patient with a recurrent tumor is alive. Median survival of all 17 patients was 94 months. Progressive disease after definitive RT occurred after a median of 11 months. CONCLUSION: Esthesioneuroblastomas are radiocurable tumors. In correlation to literature a primarily complete tumor resection followed by adjuvant RT (50-60 Gy) offers the best disease free survival.

Adult↗
PubMed2001

Three-dimensional analysis of nonhuman primate trabecular architecture using micro-computed tomography.

Until recently, detailed analyses of the architecture of nonhuman primate cancellous bone have not been possible due to a combination of methodological constraints, including poor resolution imaging or destructive protocols. The development of micro-computed tomography (microCT) and morphometric methods associated with this imaging modality offers anthropologists a new means to study the comparative architecture of cancellous bone. Specifically, microCT will allow anthropologists to investigate the relationship between locomotor behavior and trabecular structure. We conducted a preliminary study on the trabecular patterns in the proximal humerus and femur of Hylobates lar, Ateles paniscus, Macaca mulatta, and Papio anubis to investigate the quantitative differences in their trabecular architecture and evaluate the potential of microCT in anthropological inquiry. MicroCT allows the researcher to evaluate variables beyond simple two-dimensional orientations and radiographic densities. For example, this methodology facilitates the study of trabecular thickness and bone volume fraction using three-dimensional data. Results suggest that density-related parameters do not reliably differentiate suspensory-climbing species from quadrupedal species. However, preliminary results indicate that measurements of the degree of anisotropy, a measure of trabecular orientation uniformity, do distinguish suspensory-climbing taxa from more quadrupedal species. The microCT method is an advance over conventional radiography and medical CT because it can accurately resolve micron-sized struts that make up cancellous bone, and from these images a wide array of parameters that have been demonstrated to be related to cancellous bone mechanical properties can be measured. Methodological problems pertinent to any comparative microCT study of primate trabecular architecture are discussed.

Animals↗
PubMed2001

Exogenously regulated stem cell-mediated gene therapy for bone regeneration.

Regulated expression of transgene production and function is of great importance for gene therapy. Such regulation can potentially be used to monitor and control complex biological processes. We report here a regulated stem cell-based system for controlling bone regeneration, utilizing genetically engineered mesenchymal stem cells (MSCs) harboring a tetracycline-regulated expression vector encoding the osteogenic growth factor human BMP-2. We show that doxycycline (a tetracycline analogue) is able to control hBMP-2 expression and thus control MSC osteogenic differentiation both in vitro and in vivo. Following in vivo transplantation of genetically engineered MSCs, doxycycline administration controlled both bone formation and bone regeneration. Moreover, our findings showed increased angiogenesis accompanied by bone formation whenever genetically engineered MSCs were induced to express hBMP-2 in vivo. Thus, our results demonstrate that regulated gene expression in mesenchymal stem cells can be used as a means to control bone healing.

Animals↗
PubMed2001

Targeting of adenovirus to endothelial cells by a bispecific single-chain diabody directed against the adenovirus fiber knob domain and human endoglin (CD105).

The use of adenoviruses for antivascular cancer gene therapy is limited by their low transduction efficiency for endothelial cells. We have developed a recombinant bispecific antibody as a molecular bridge, linking the adenovirus capsid to the endothelial cell surface protein endoglin, for vascular targeting of adenoviruses. Endoglin (CD105), a component of the transforming growth factor beta receptor complex, represents a promising target for antivascular cancer therapy. Endoglin is expressed predominantly on endothelial cells and is upregulated in angiogenic areas of tumors. We isolated single-chain Fv fragments directed against human endoglin from a human semisynthetic antibody library. One of the isolated scFv fragments (scFv C4) bound specifically to various proliferating primary endothelial cells or cell lines including HUVEC, HDMEC, HMVEC, and HMEC. ScFv C4 was therefore used to construct a bispecific single-chain diabody directed against endoglin and the adenovirus fiber knob domain (scDb EDG-Ad). This bispecific molecule mediated enhanced and selective adenovirus transduction of HUVECs, which was independent from binding to the coxsackievirus and adenovirus receptor (CAR) and alpha(v)-integrins. Thus, adenovirus infection was redirected to a new cellular receptor (CD105) and cell entry pathway. These results demonstrate the utility of bispecific single-chain diabodies, which can be produced in large quantities in bacteria, for the retargeting of adenoviruses in cancer gene therapy.

Adenoviridae↗
PubMed2001

The polycyclic musk 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthaline lacks liver tumor initiating and promoting activity in rats exposed to human-relevant doses.

7-Acetyl-1,1,3,4,4,6-hexamethyl- 1,2,3,4-tetra-hydronaphthaline (AHTN) is one of the two most widely used fragrances of a group of substances known collectively as the polycyclic musks. In the last few years evidence has been accumulating that AHTN is hepatotoxic when administered at high doses. In the present study the subchronic hepatotoxicity of AHTN administered to rats at doses within the human exposure range was evaluated. For this purpose female and male juvenile Wistar rats were exposed to AHTN (300 microg/kg body weight per day, i.p.) alone or to a single dose of diethylnitrosamine (DEN) (100 mg/kg body weight, i.p.) followed by AHTN (1, 10, 100 or 300 microg/kg body weight per day, i.p.) for 90 days. Thereafter the liver architecture as well as the presence of placental glutathione S-transferase (GST-P)-positive hepatic lesions was assessed. In male animals receiving AHTN alone or in combination with DEN the number of GST-P-positive single hepatocytes was similar to that in untreated rats, while GST-P-positive mini-foci and foci were not observed. In the case of female rats the number of GST-P-positive single hepatocytes and mini-foci in AHTN-treated rats was similar to that in untreated animals, whereas in those animals receiving AHTN either alone or in combination with DEN, GST-P-positive foci could not be detected or were present in a number as similar to that in untreated rats. In conclusion, in the present study it has been shown that AHTN administered over a 90-day period in concentrations similar to those taken up daily by humans does not lead to hepatotoxicity.

Animals↗
PubMed2001

Determination of the kinetic parameters of the phenol-degrading thermophile Bacillus themoleovorans sp. A2.

Phenolic compounds are pollutants in many wastewaters, e.g. from crude oil refineries, coal gasification plants or olive oil mills. Phenol removal is a key process for the biodegradation of pollutants at high temperatures because even low concentrations of phenol can inhibit microorganisms severely. Bacillus thermoleovorans sp. A2, a recently isolated thermophilic strain (temperature optimum 65 degrees C), was investigated for its capacity to degrade phenol. The experiments revealed that growth rates were about four times higher than those of mesophilic microorganisms such as Pseudomonas putida. Very high specific growth rates of 2.8 h(-1) were measured at phenol concentrations of 15 mg/l, while at phenol concentrations of 100-500 mg/l growth rates were still in the range of 1 h(-1). The growth kinetics of the thermophilic Bacillus thermoleovorans sp. A2 on phenol as sole carbon and energy source can be described using a three-parameter model developed in enzyme kinetics. The yield coefficient Yx/s of 0.8-1 g cell dry weight/g phenol was considerably higher than cell yields of mesophilic bacteria (Yx/s 0.40-0.52 g cell dry weight/g phenol). The highest growth rate was found at pH 6. Bacillus thermoleovorans sp. A2 was found to be insensitive to hydrodynamic shear stress in stirred bioreactor experiments (despite possible membrane damage caused by phenol) and flourished at an ionic strength of the medium of 0.25(-1) mol/l (equivalent to about 15-60 g NaCl/l). These exceptional properties make Bacillus thermoleovorans sp. A2 an excellent candidate for technical applications.

Bacillus↗
PubMed2001

The effect of an osteolytic tumor on the three-dimensional trabecular bone morphology in an animal model.

OBJECTIVE: To investigate the application of micro-computed tomography (microCT) for the assessment of density differences and deterioration of three-dimensional architecture of trabecular bone in an experimental rat model for tumor-induced osteolytic defects. DESIGN AND MATERIALS: Walker carcinosarcoma 256 malignant breast cancer cells (W256) were surgically implanted into the medullary canal of the left femur of 15 4-month-old rats. Twenty-eight days after surgery all animals were killed and both femora from each rat were harvested. A total of 30 specimens (left and right femur) were scanned in a desktop microCT imaging system (microCT 20, Scanco Medical) to assess densitometric and architectural parameters. For each specimen a total of 200 micro-tomographic slices with a resolution of 30 microns in the distal metaphysis was taken. Bone mineral content (BMC) was analyzed for both cortical and trabecular bone (ctBMC), and for trabecular bone only (tBMC). Architectural indices (BV/TV, Tb.N, Tb.Th, Tb.Sp) according to standard definitions used in histomorphometry were calculated for trabecular bone. RESULTS: The quantitative analysis of density parameters revealed significantly (P < 0.001) lower values for ctBMC and tBMC in the tumor-bearing group (T) of 26% and 31%, respectively, compared with the contralateral control group. The quantitative analysis revealed significant (P < 0.001) changes in the architectural parameters in the tumor-bearing bones compared with the contralateral control group: BV/TV was 30% lower, Tb.N and BS/TV decreased by 24% and 21%, respectively, Tb.Th. decreased by 10% and Tb.Sp. increased by 94%. CONCLUSIONS: This study demonstrates that microCT is able to provide three-dimensional parameters of bone mass and trabecular structure in an animal model for tumor-induced bone loss. Recent advances in therapeutic approaches for skeletal diseases such as osteoporosis and metastatic bone diseasse rely on an understanding of the effects of the agents on the mechanical properties of bone. In order to quantify the structural changes of the affected bones the application of a non-destructive method is mandatory. The use of microCT seems to be a great advantage, since biomechanical tests and further histologic analysis can be done for the same specimens.

Animals↗
PubMed2001

Modulation of growth factor binding properties of alpha2-macroglobulin by enzyme therapy.

PURPOSE: To investigate the binding of transforming growth factor-beta (TGF-beta) to human alpha2-macroglobulin upon oral treatment of patients with proteases. METHODS: Volunteers were given a cocktail of active proteinases (Phlogenzym) composed of trypsin, bromelain and the additive rutoside orally over a period of 7 days at low dose followed by a bolus application. Before and after medication plasma was immediately withdrawn and binding of 125I-TGF-beta to the proteinase inhibitor alpha2-macroglobulin was determined by electrophoresis and gamma-counting. Cell culture experiments were performed to study the effect of transformed alpha2-macroglobulin on TGF-beta-stimulated proliferation of skin fibroblasts. RESULTS: Ingestion of proteinases was found to trigger the formation of intermediate forms of alpha2-macroglobulin displaying high affinity to TGF-beta. Maximum binding of TGF-beta was observed 1-2 h after bolus ingestion, and steadily levelled off with time. In vitro experiments demonstrated that complex formation of diverse proteinases (trypsin, alpha-chymotrypsin, bromelain and plasmin) with alpha2-macroglobulin conferred binding of 125I-TGF-beta, alpha2-Macroglobulin transformed by methylamine or proteinases was found to abolish the TGF-beta effect on fibroblasts in cell culture. CONCLUSIONS: Intestinal absorption of proteinases triggers the formation of TGF-beta binding species of alpha2-macroglobulin in blood. Mediated by this process high concentrations of TGF-beta might be reduced via enhanced clearance of alpha2-macroglobulin-TGF-beta complexes. Thus, proteinase therapy may have beneficial effects in treatment of fibrosis and certain cancers accompanied by excessively high TGF-beta concentrations.

Administration, Oral↗
PubMed2001

[Embolism prevention during interventional treatment of aortocoronary bypass stenoses].

No-reflow is an unpredictable complication after percutaneous intervention in saphenous vein grafts. Plaque embolism, vasoconstriction and thrombosis are mechanisms that lead to poor distal run-off. Treatments with alternative techniques like DCA, TEC and ELCA as well as phamacological attempts like GP IIb/IIIA inhibitors, vasodilators and calcium-channel blockers do not improve outcome. This is the rationale for the development of mechanical devices to prevent distal embolization. Two concepts of distal protection devices are currently realized: occlusive balloon and filtering devices. The largest experience comes from the PercuSurge GuardWire, an occlusive balloon device. The recently presented data from the SAFER trial showed a significant prevention of distal embolization and improvement in clinical outcome. The second generation of filter devices is under investigation; the advantages of these systems are the preservation of blood flow and precise angiography-guided stent positioning. Another issue of investigation is a broader use of protection devices in carotid stenting, and in interventions in acute MI and acute coronary syndromes.

Aged↗
PubMed2001

Quality of life of patients with laryngeal carcinoma: a post-treatment study.

This study was designed to determine the quality of life of patients successfully treated for laryngeal cancer. A questionnaire was mailed to 233 patients. A total of 124 responses were suitable for analysis. The questionnaire consisted of three components: sociodemographic data, European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Core Questionnaire (QLQ - C 30, version 2.0), and EORTC QLQ, Head and Neck Module (H & N 35). The assessment included five treatment groups: chordectomy, partial laryngectomy, irradiation as primary therapy, laryngectomy, laryngectomy and radiotherapy. The evaluation for the functional scales of the EORTC QLQ - C 30 resulted in a higher quality of life of patients with maintained larynx in comparison to laryngectomised patients. In the symptom scales, patients after laryngectomy and/or radiotherapy suffered more from fatigue, pains and appetite loss. Laryngectomees stated more financial difficulties. The evaluation of the ENT-specific EORTC module showed that patients after laryngectomy had more symptoms. Typical symptoms after radiotherapy were a dry mouth, sticky saliva and coughing. Noticeably, no differences existed among the several groups with regard to voice production. The EORTC QLQ- H & N 35 does not appear to be sensitive enough to assess this parameter.

Adult↗
PubMed2001

TRANCE/RANKL knockout mice are protected from bone erosion in a serum transfer model of arthritis.

There is considerable evidence that osteoclasts are involved in the pathogenesis of focal bone erosion in rheumatoid arthritis. Tumor necrosis factor-related activation-induced cytokine, also known as receptor activator of nuclear factor-kappaB ligand (TRANCE/RANKL) is an essential factor for osteoclast differentiation. In addition to its role in osteoclast differentiation and activation, TRANCE/RANKL also functions to augment T-cell dendritic cell cooperative interactions. To further evaluate the role of osteoclasts in focal bone erosion in arthritis, we generated inflammatory arthritis in the TRANCE/RANKL knockout mouse using a serum transfer model that bypasses the requirement for T-cell activation. These animals exhibit an osteopetrotic phenotype characterized by the absence of osteoclasts. Inflammation, measured by clinical signs of arthritis and histopathological scoring, was comparable in wild-type and TRANCE/RANKL knockout mice. Microcomputed tomography and histopathological analysis demonstrated that the degree of bone erosion in TRANCE/RANKL knockout mice was dramatically reduced compared to that seen in control littermate mice. In contrast, cartilage erosion was present in both control littermate and TRANCE/RANKL knockout mice. These results confirm the central role of osteoclasts in the pathogenesis of bone erosion in arthritis and demonstrate distinct mechanisms of cartilage destruction and bone erosion in this animal model of arthritis.

Animals↗
PubMed2001

Correlation of thoracic and lumbar vertebral failure loads with in situ vs. ex situ dual energy X-ray absorptiometry.

In this study we explore the hypothesis that estimates of failure loads in the thoracic spine by lumbar dual energy X-ray absorptiometry (DXA) are compromised of skeletal heterogeneity throughout the spine and artifacts of spinal DXA. We studied the correlation between mechanical failure loads of thoracic and lumbar vertebrae, and that of in situ vs. ex situ lumbar DXA with thoracic and lumbar fracture loads, respectively. One hundred and nineteen subjects (76 female, age 82+/-9yr; 43 male, age 77+/-11yr) were examined under in situ conditions (anterior-posterior direction), the scans being repeated ex situ (lateral projection) in 68 cases. The failure loads of thoracic vertebrae (T) 6 and 10, and lumbar vertebra (L) 3 were determined in axial compression, using a functional 3-segment unit. The correlation between thoracic failure loads (T6 vs. T10) was significantly (p<0.01) higher (r=0.85) than those between thoracic and lumbar vertebrae (r=0.68 and 0.61, respectively). Lateral ex situ DXA displayed a significantly higher correlation (p<0.05) with lumbar vertebral fracture loads than in situ anterior-posterior DXA (r=0.85 vs. 0.71), but the correlation of thoracic failure loads with lateral ex situ lumbar DXA was similar to that obtained in situ in anterior-posterior direction (r=0.69 vs. 0.69 for T10, and r=0.61 vs. 0.65 for T6). The correlation between fracture loads of different spinal segments, and between DXA and failure loads was not significantly different between men and women. The results demonstrate a substantial heterogeneity of mechanical competence throughout the spine in elderly individuals. Because of the high incidence of fractures in the thoracic spine, these findings suggest that, clinically, lateral DXA involves no relevant advantage over anterior-posterior measurements of the lumbar spine.

Absorptiometry, Photon↗
PubMed2001

Novel features in a combined polyketide synthase/non-ribosomal peptide synthetase: the myxalamid biosynthetic gene cluster of the myxobacterium Stigmatella aurantiaca Sga15.

BACKGROUND: Myxobacteria have been well established as a potent source for natural products with biological activity. They produce a considerable variety of compounds which represent typical polyketide structures with incorporated amino acids (e.g. the epothilons, the myxothiazols and the myxalamids). Several of these secondary metabolites are effective inhibitors of the electron transport via the respiratory chain and have been widely used. Molecular cloning and characterization of the genes governing the biosynthesis of these structures is of considerable interest, because such information adds to the limited knowledge as to how polyketide synthases (PKSs) and non-ribosomal peptide synthetases (NRPSs) interact and how they might be manipulated in order to form novel antibiotics. RESULTS: A DNA region of approximately 50000 base pairs from Stigmatella aurantiaca Sga15 was sequenced and shown by gene disruption to be involved in myxalamid biosynthesis. Sequence analysis reveals that the myxalamids are formed by a combined PKS/NRPS system. The terminal NRPS MxaA extends the assembled polyketide chain of the myxalamids with alanine. MxaA contains an N-terminal domain with homology to NAD binding proteins, which is responsible during the biogenesis for a novel type of reductive chain release giving rise to the 2-amino-propanol moiety of the myxalamids. The last module of the PKS reveals an unprecedented genetic organization; it is encoded on two genes (mxaB1 and mxaB2), subdividing the domains of one module from each other. A sequence comparison of myxobacterial acyl-transferase domains with known systems from streptomycetes and bacilli reveals that consensus sequences proposed to be specific for methylmalonyl-CoA and malonyl-CoA are not always reliable. CONCLUSIONS: The complete biosynthetic gene cluster of the myxalamid-type electron transport inhibitor from S. aurantiaca Sga15 has been cloned and analyzed. It represents one of the few examples of combined PKS/NRPS systems, the analysis and manipulation of which has the potential to generate novel hybrid structures via combinatorial biosynthesis (e.g. via module-swapping techniques). Additionally, a new type of reductive release from PKS/NRPS systems is described.

Amino Acid Sequence↗
PubMed2001

Measurement of cancellous bone strain during mechanical tests using a new extensometer device.

A device for measuring mid-substance strain in bone during uniaxial compression was developed with special attention to subsequent FE modelling. It is based on dual instrumented cantilever arms that measure the difference in tip-to-tip deflection. The so-called extensometer device was compared to two standard methods of measuring strain based on platen measurements. The extensometer device output was highly linear with tip deflection (r(2)>0.99), and contact of the devices with the specimen was optimized by using an axial distribution of three devices fixed in a free-floating jig. Deflection of the extensometer arms was accurate to 4.8 microm, and precision was between 2-5 microm. Tests included measuring rubber test specimens and cylindrical cancellous bone cores extracted from canine femoral condyles. A trend of decreasing apparent modulus with decreasing strain rate was evident with the extensometer technique. Correlation between the extensometer method and the other two methods was r(2)=0.55. The measure of mid-substance strain avoids non-linearities in the compression tests caused by early failure at the specimen ends, and the uniaxial testing conditions result in boundary conditions that are well suited for subsequent finite element analysis.

Animals↗
PubMed2001

Highly efficient transduction of endothelial cells by targeted artificial virus-like particles.

Targeting the tumor vasculature by gene therapy is a potentially powerful approach, but suitable vectors have not yet been described. We have designed a new type of liposomal vector, based on the composition of anionic retroviral envelopes, that is serum-resistant and nontoxic. These artificial virus-like envelopes (AVEs) were endowed with a cyclic RGD-containing peptide as a targeting device for the a(v)beta3-integrin on tumor endothelial cells (ECs). The packaging of plasmid DNA complexed with low-molecular-weight, nonlinear polyethyleneimine into these AVEs yielded artificial virus-like particles (AVPs) that transduced ECs with efficiencies of up to 99%. In contrast, transduction of a variety of other cell types by these RGD-AVPs was comparably inefficient under the same experimental conditions. This EC selectivity was mediated, in part, but not exclusively, by the RGD ligand, as suggested by the reduced, but still relatively high, transduction efficiency seen with AVPs lacking RGD. The interaction of anionic lipids of the AVPs with ECs may therefore contribute to the observed selective and highly efficient transduction of this cell type. These findings suggest that the targeted AVE technology is a useful approach to create highly efficient nonviral vectors.

Antineoplastic Agents↗
PubMed2001

A synthetic leucine zipper-based dimerization system for combining multiple promoter specificities.

One of the biggest challenges facing gene therapy is the development of vectors that direct the activity of therapeutic genes specifically to the sites of disease. To achieve this goal, the restriction of transgene transcription via synthetic promoters that are endowed with multiple specificities represents a particularly promising strategy. Towards this end, we have developed a generally applicable strategy (DCTF system) where a synthetic promoter is driven by an artificial heterodimeric transcription factor whose DNA-binding and transactivating subunits are expressed from two promoters with different selectivity. A crucial determinant of the DCTF system is the heterodimerization interface that should provide for a high affinity interaction without interference by endogenous proteins. Here, we describe such a dimerization system based on engineered Fos and Jun leucine zippers. We show the usefulness of this system for the combination of cell type-specific and cell cycle-regulated transcription and demonstrate its functionality in an in vivo setting.

Animals↗
PubMed2001

Cell surface display of a lysosomal enzyme for extracellular gene-directed enzyme prodrug therapy.

Prodrug conversion is a promising approach to cytotoxic gene therapy if an efficient transfer of the generated drug to adjacent cells can be achieved. To maximize the efficacy of this strategy we sought to develop a system that is based on a human enzyme, acts extracellularly yet in close vicinity of the transduced cell and can be used with multiple prodrugs. Results obtained with a secreted version of human beta-glucuronidase suggested that this enzyme could be a suitable candidate, although a more stringent retention of the enzyme at the site of the producer cell, such as its attachment to the cell surface, would be desirable. Here, we show that the fusion of the transmembrane domain of the human PDGF receptor to a C-terminally truncated form of human beta-glucuronidase results in its surface accumulation at high steady-state levels. Using a doxorubicin prodrug, we demonstrate that this GDEPT system produces a strong bystander effect and has potent antitumor activity in vivo.

Animals↗