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Biomedical subjects

M Wagner

Publications and source records attributed to M Wagner.

At least 307 records · Page 17Linked to original sources
PubMed1998

Transfection of the type I TGF-beta receptor restores TGF-beta responsiveness in pancreatic cancer.

Transforming growth factor-beta (TGF-beta) signaling is initiated following heterodimerization of the type II TGF-beta receptor (TbetaRII) with the type I TGF-beta receptor (TbetaRI). Both receptors are required for TGF-beta responsiveness. In the present study, we characterized the actions of TGF-beta1 in T3M4 human pancreatic cancer cells, which express low levels of TbetaRI and high levels of TbetaRII. Cells were transiently transfected with p3TP-Lux, a TGF-beta-responsive luciferase reporter gene construct. TGF-beta1 was without effect in parental T3M4 cells, but caused a time- and dose-dependent increase in luciferase activity in T3M4 cells co-transfected with a TbetaRI cDNA expression vector. Co-transfection of TbetaRI with a truncated Smad4 cDNA that is known to block TGF-beta-dependent signaling, abrogated the TbetaRI-induced increase in luciferase activity. Sequencing of the TbetaRI and the Smad4 genes in T3M4 cells did not reveal any mutations. These findings indicate that one mechanism for TGF-beta resistance in pancreatic cancer is due to a quantitative decrease in TbetaRI expression.

Activin Receptors, Type I↗
PubMed1998

Effects of anticonvulsive drugs on pentylenetetrazol kindling and long-term potentiation in freely moving rats.

Drugs with anticonvulsive properties and different mechanisms of action were compared for their influence on long-term potentiation and pentylenetetrazol kindling in freely moving animals. Rats were chronically implanted with a stimulation electrode in the angular bundle and a recording electrode in the dentate gyrus. Field potentials in the dentate gyrus were elicited and long-term potentiation was induced by stimulation of the perforant pathway. The clinically used drugs or the potentially anticonvulsive drugs, diphenylhydantoin (50 mg/kg), diazepam (0.5 mg/kg), pentobarbital (10 mg/kg), dizocilpine (MK 801, 0.2 mg/kg) and CGP 43487 (2-amino-4-methyl-5-phosphono-3-pentenoic acid-carboxyethylester, 10 mg/kg), were injected before tetanization. In behavioural experiments pentylenetetrazol kindling was performed with pretreatment with the substances in dosages indicated above (except MK 801, 0.3 mg/kg). Field potentials recorded in the interval between drug administration and tetanization were influenced only by diphenylhydantoin which enhanced the population spike amplitude to 128% of control values. However, the substances showed different effects on long-term potentiation. MK 801, CGP 43487 and pentobarbital depressed potentiation; diazepam was without effect. Diphenylhydantoin had a minor influence on induction but significantly impaired maintenance of long-term potentiation. Furthermore, MK 801, CGP 43487, diazepam and pentobarbital differentially depressed kindling whereas phenytoin only slightly influenced it. The consequences as to hypothetical common cellular mechanisms for kindling development and long-term potentiation are discussed.

Animals↗
PubMed1998

In situ detection of a virulence factor mRNA and 16S rRNA in Listeria monocytogenes.

Simultaneous in situ analysis of the structure and function of bacterial cells present within complex communities is a key for improving our understanding of microbial ecology. A protocol for the in situ identification of Listeria spp. using fluorescently tagged, rRNA-targeted oligonucleotide probes was developed. Ethanol fixation and enzymatic pretreatment with lysozyme and proteinase K were used to optimize whole cell hybridization of exponential phase and stationary phase Listeria spp. cells. In parallel, transcript probes carrying multiple digoxigenin molecules were combined with anti-digoxigenin Fab antibody fragments labeled with horseradish peroxidase to detect, via the catalytic deposition of fluorescein-tyramide, the iap-mRNA in single Listeria monocytogenes cells. The iap gene encodes the associated virulence factor p60. Application of the new signal amplification technique resulted in strong signals comparable in intensity to those obtained with fluorescently labeled rRNA-targeted oligonucleotide probes.

Bacterial Proteins↗
PubMed1998

Three-dimensional computer assisted magnetic resonance imaging for neurosurgical planning in parasagittal and parafalcine central region tumors.

Usually, conventional magnetic resonance spin echo images (MRI) are sufficient to establish the diagnosis of intracranial pathology. Planning and executing a neurosurgical procedure requires the ability of the neurosurgeon to transform these two-dimensional MRI into a three-dimensional (3-D) virtual image of the pathology and the surrounding neuronal anatomy. Such mentally performed transformations after sequential observation of the individual two-dimensional slices (i.e., MRI and angiography) may be virtual tasks that are very difficult or sometimes impossible to achieve. Using 3-D MRI data sets and a semiautomatic computer assisted segmentation technique, we tried to simulate intraoperative situs-based 3-D MRI reconstructions of parasagittal and parafalcine central region tumors. The MRI reconstructions were integrated into the neurosurgical planning procedure as an additional tool. They proved to be an important adjunct in determining the distinct anatomy of the intracranial pathology in its relation to the surrounding and overlying brain and vascular (especially venous) anatomy. With 10 patients with central region parasagittal and parafalcine tumors, we found that the 3-D MRI reconstructions revealed additional information compared to conventional cross-sectional images and had an influence on neurosurgical planning and strategy, improving neurosurgical performance and patient outcome.

Humans↗
PubMed1998

Evaluation of locus heterogeneity and EXT1 mutations in 34 families with hereditary multiple exostoses.

Hereditary multiple exostoses (EXT) is an autosomal dominant disorder characterized by growth of benign bone tumors. Three chromosomal loci have been implicated in this genetically heterogeneous disease: EXT1 at 8q24, EXT2 at 11p13, and EXT3 on 19p. EXT1 and EXT2 were recently cloned. We evaluated 34 families with EXT to estimate the proportion of disease attributable to EXT1, EXT2, and EXT3 and to investigate the spectrum of EXT1 mutations. Linkage analyses combined with heterogeneity testing provides strong evidence in favor of linkage of disease to both chromosomes 8 and 11, but does not support evidence of linkage to chromosome 19 in this data set. The 11 EXT1 exons were PCR-amplified and sequenced in all 11 isolated cases and in 20 of the 23 familial cases. Twelve different novel EXT1 mutations were detected, including 5 frame-shift deletions or insertions, 1 codon deletion, and 6 single base-pair substitutions distributed across 8 of the exons. Only 2 of the mutations were detected in more than one family. Three mutations affect sites in which alterations were previously reported. Nonchain-terminating missense mutations were identified in codons 280 and 340, both coding for conserved arginine residues. These residues may be crucial to the function of this protein. Although the prevalence of EXT has been estimated to be approximately 1/50,000 individuals, the disease has been reported to occur much more frequently in the Chamorro natives on Guam. Our detection of an EXT1 mutation in one Chamorro subject will allow investigation of a possible founder effect in this population. Combined mutational and heterogeneity analyses in this set of families with multiple exostoses suggest that 66% of our total sample, including 45% of isolated and 77% of familial cases, are attributable to abnormalities in EXT1.

Chromosomes, Human, Pair 11↗
PubMed1998

MR-microscopic visualization of anisotropic internal cartilage structures using the magic angle technique.

NMR microscopic studies of articular cartilage at 7.1 T are presented. Using a special experimental design, T2-weighted spin-echo images of cartilage-bone plugs were taken under variable angles with respect to the static magnetic field B0 to visualize the angular-dependent representation of internal matrix structures mediated by the collagen network arrangement. To quantify the observed orientational effect in the MR images, exact measurements of the transverse relaxation time T2 were taken using the CPMG sequence. The NMR experiments show the strong influence of the cartilage orientation with respect to the static magnetic field on the inhomogeneous appearance of the articular cartilage in the MR image. Additionally performed polarization light microscopic investigations demonstrate the direct relation between the oriented collagenous structures and the anisotropic regions observed in the MR images. A simple cartilage matrix model derived from the experimental findings is proposed, and consequences for the clinical assessment of the articular joint are discussed.

Aged↗
PubMed1998

Pharmacokinetic and pharmacodynamic evaluation of fluticasone propionate after inhaled administration.

OBJECTIVE: To evaluate the pharmacokinetic and systemic pharmacodynamic properties of inhaled fluticasone propionate (FP). METHODS: Single doses of 0.25, 0.5, 1.0 and 3.0 mg FP were administered to groups of six healthy subjects. Serum concentration profiles of FP were monitored over 24 h by means of high-performance liquid chromatography/mass spectrometry (HPLC/MS-MS). Systemic pharmacodynamic effects were evaluated by measuring endogenous serum cortisol and circulating white blood cells, and analyzed with previously developed integrated pharmacokinetic/pharmacodynamic (PK/PD) models. RESULTS: FP showed a dose-independent terminal half-life with a mean (SD) of 6.0 (0.7) h. Maximum serum concentrations occurred 1.0 (0.5) h after administration, ranging from 90 pg.ml(-1) for the 0.25 mg dose to 400 pg.ml(-1) for the 3.0 mg dose. This, together with an estimated mean absorption time of nearly 5 h and a known oral bioavailability of less than 1%, indicates prolonged residence at and slow absorption from the lungs. In the investigated dose range, the cumulative systemic effect was dose-dependent for both markers of pharmacodynamic activity. For doses of 0.25, 0.50, 1.0 and 3.0 mg FP, the PK/PD-based cumulative systemic-effect parameters were 159, 186, 257 and 372% .h for lymphocyte suppression, 107, 186, 202 and 348% .h for granulocyte induction and 23.6%, 33.8%, 51.0% and 73.6% for cortisol reduction, respectively. The time courses of lymphocytes, granulocytes and endogenous cortisol could be sufficiently characterized with the applied PK/PD models. The measured in vivo EC50 values, 30 pg.ml(-1) and 7.3 pg.ml(-1) for white blood cells and cortisol, respectively, were in good agreement with predictions based on the in vitro relative receptor affinity of FP. CONCLUSION: After inhalation, FP follows linear pharmacokinetics and exhibits dose-dependent systemic pharmacodynamic effects that can be described by PK/PD modeling.

Administration, Inhalation↗
PubMed1998

Improving source reconstructions by combining bioelectric and biomagnetic data.

OBJECTIVES: A framework for combining bioelectric and biomagnetic data is presented. The data are transformed to signal-to-noise ratios and reconstruction algorithms utilizing a new regularization approach are introduced. METHODS: Extensive simulations are carried out for 19 different EEG and MEG montages with radial and tangential test dipoles at different eccentricities and noise levels. The methods are verified by real SEP/SEF measurements. A common realistic volume conductor is used and the less well known in vivo conductivities are matched by calibration to the magnetic data. Single equivalent dipole fits as well as spatio-temporal source models are presented for single and combined modality evaluations and overlaid to anatomic MR images. RESULTS: Normalized sensitivity and dipole resolution profiles of the different EEG/MEG acquisition systems are derived from the simulated data. The methods and simulations are verified by simultaneously measured somatosensory data. CONCLUSIONS: Superior spatial resolution of the combined data studies is revealed, which is due to the complementary nature of both modalities and the increased number of sensors. A better understanding of the underlying neuronal processes can be achieved, since an improved differentiation between quasi-tangential and quasi-radial sources is possible.

Brain Mapping↗
PubMed1998

Malignant transformation of duct-like cells originating from acini in transforming growth factor transgenic mice.

BACKGROUND & AIMS: In transgenic mice overexpressing transforming growth factor (TGF)-alpha in the exocrine pancreas, progressive pancreatic fibrosis and a transdifferentiation of acinar cells to duct-like cells occurs. The present study was undertaken to analyze this transdifferentiation process. METHODS: Pancreatic specimens were characterized using light microscopy and immunohistochemistry. Expression of the epidermal growth factor receptor (EGFR) and TGF-alpha was evaluated with slot blot and Western analysis. To identify other generic events, K-ras mutations were screened with an enriched polymerase chain reaction approach and p53 expression was detected with immunohistochemistry. RESULTS: Morphological examination revealed an aggregation of interlobular fibroblasts and a decrease in acinar cell height starting at day 14 after birth. In older animals, these acinar cells change to duct-like cells, which form tubular structures and express ductal markers. Evidence for dysplastic changes was found in 12 of 21 TGF-alpha transgenic mice older than 1 year. We also observed four malignant pancreatic tumors, which were multicentric and originated from dysplastic tubular complexes. They displayed a mixed cystic-papillary phenotype strongly positive for carbonic anhydrase activity. EGFR expression progressively increased in the transition from acinar to duct-like and transformed cells. Activating K-ras mutations could not be detected; however, tubular complexes and tumors displayed increased immunoreactivity for nuclear p53. CONCLUSIONS: These data suggest an involvement of the TGF-alpha/EGFR pathway in conjunction with other yet unknown events in pancreatic tumor development. Furthermore, these observations are in favor of an acinar-ductal carcinoma sequence. Thus, these transgenic animals will be useful to define genetic alterations associated with a transition from acinar cells to a neoplastic ductal phenotype.

Animals↗
PubMed1998

Suppression of fibroblast growth factor receptor signaling inhibits pancreatic cancer growth in vitro and in vivo.

BACKGROUND & AIMS: Fibroblast growth factors (FGFs) are mitogenic polypeptides that activate specific cell surface FGF receptors (FGFRs). Pancreatic cancers overexpress basic FGF (bFGF) and the type I FGF receptor (FGFR-1), and overexpression of bFGF has been correlated with decreased patient survival. The aim of this study was to examine the effects of abrogation of FGFR-1-dependent signaling on pancreatic cancer cell growth. METHODS: PANC-1 human pancreatic cancer cells were transfected with a truncated FGFR-1 complementary DNA (FGFR405), resulting in the expression of a kinase-deficient receptor. Activation of endogenous FGFR-1 was assessed in immunoblot studies with antiphosphotyrosine and anti-active mitogen-activated protein (MAP) kinase antibodies. Effects on cell growth were determined in vitro and in nude mice. RESULTS: PANC-1 clones expressing the truncated receptor showed attenuated receptor tyrosine phosphorylation and MAP kinase activation in response to bFGF, decreased basal cell growth, and a marked decrease in tumor-forming potential in vivo. Confirmatory experiments with MIA PaCa-2 pancreatic cancer cells indicated that FGFR405 also attenuated FGF-dependent MAP kinase activation in this cell line. CONCLUSIONS: The findings suggest that FGFR-dependent signaling is crucial for pancreatic cancer growth and raise the possibility that inhibition of FGFR signaling may ultimately prove useful as a therapeutic option in patients with pancreatic cancer.

Animals↗
PubMed1998

High-versus low-dose erythropoietin in extremely low birth weight infants. The European Multicenter rhEPO Study Group.

OBJECTIVE: To investigate whether a weekly 1500 IU/kg dose of recombinant human erythropoietin (rhEPO) is more effective than a dose of 750 IU/kg/week in preventing anemia and reducing the transfusion need in infants with birth weights less than 1000 gm. STUDY DESIGN: In a randomized, double-blind, multicenter trial, 184 infants with birth weights between 500 and 999 gm were treated with either rhEPO 750 (low-dose group) or 1500 IU/kg/week (high-dose group) from day 3 of life until 37 weeks' corrected age. RESULTS: Thirty-two percent of the infants in each group did not receive any transfusion during the treatment period. The total volume of erythrocytes received was similar in each group. The success rate, defined as no transfusion needed and hematocrit value 0.30 L/L or greater, was 27.6% in the low-dose and 29.5% in the high-dose group (p = 0.96). CONCLUSION: Doubling the rhEPO dose of 750 IU/kg/week is not indicated in infants with birth weights less than 1000 gm.

Anemia↗
PubMed1998

Effect of selected environmental factors on degradation and mineralization of biaryl compounds by the bacterium Ralstonia pickettii in soil and compost.

By varying selected environmental factors, the degradation and mineralization of biaryl compounds by the bacterium Ralstonia pickettii in soil and compost were investigated. An optimized soil moisture and enhanced bioavailability by using the nonionic surfactant Tween 80 were of great importance for the degradation rates of biaryl compounds like biphenyl and 4-chlorobiphenyl by cells of Ralstonia picketti SBUG 290 inoculated into soil. Additionally, degradation of these compounds by the investigated strain in soil was strongly dependent upon the medium of precultivation. Also the influence of temperature and soil pH-value was tested. In contrast to the used soil, the autochthonous flora of the compost seemed to have a higher physiological activity. All investigated compounds (biphenyl, 4-chlorobiphenyl and dibenzofuran) were degraded quickly in compost. Inoculation with the investigated bacterium did not enhance the degradation rates significantly.

Air Pollutants, Occupational↗
PubMed1998

Effects of anionic and nonionic polymers on fusion and binding of Sendai virus to human erythrocyte ghosts.

Effects of various polymers (dextran sulfate, dextran and polyethylene glycol) on binding and fusion of Sendai virus to target cells were studied by use of fluorescence spectroscopy. Direct binding of dextran sulfate but not dextran to Sendai virus was detected. Anionic and nonionic polymers showed definite effects on segmental motions of the viral envelope proteins. Sendai virus binding to human erythrocyte ghost membranes (HEG) was reduced by dextran sulfate and dextran while the fusion temperature dependence remained unaltered at approximately 20 degrees C. Nonionic polymer, polyethylene glycol, caused an increase in extent of fusion of Sendai virus with HEG. Segmental motion of viral envelope proteins, determined in terms of anisotropy of fluorescent probes attached to viral surface proteins, exhibited a temperature dependent transition at 20 degrees C by a sharp change from restricted to less restricted motion. In the presence of each of the polymers, this transition was no longer apparent. Since fusion did occur in the presence of all polymers, the temperature dependent characteristic of Sendai virus target cell fusion can be said not to depend on viral surface protein segmental motion. A reasonable and coherent explanation was given for the apparent disparity between the effects of inhibiting and enhancing polymers on fusion and motion of viral proteins.

Animals↗
PubMed1998

Vitamin E up-regulates arachidonic acid release and phospholipase A2 in megakaryocytes.

The release of arachidonic acid is the rate limiting step in eicosanoid synthesis. In mammalian cells, the release of arachidonic acid is catalyzed by several enzymes. The 85 kDa cytosolic phospholipase A2 (cPLA2) is the key enzyme for the release reaction because of its specific acyl selectivity in phospholipid substrates. We have previously reported that vitamin E enrichment potentiates the arachidonic acid release as well as the spontaneous prostacyclin release in human endothelial cells. In contrast, similar enrichment of diets caused a dose-dependent suppression of platelet thromboxane synthesis. Therefore, the present study was undertaken to determine the effect of vitamin E on arachidonate release and phospholipaseA2 activity in a platelet precursor cell, the MEG-01 megakaryocyte cell line. When these cells were incubated with different concentrations of vitamin E, cellular incorporation was linear with the dosages of this vitamin. Determination of arachidonate release after labeling cells with [3H]-arachidonate showed that vitamin E enrichment caused a dose-dependent increase in ionophore A23187-induced [3H]-arachidonic acid release. Analysis of PLA2 activity showed that activity was detected in the cytosol and this activity was completely abolished by the addition of anti-cPLA2, antibody. Determination of cPLA2 activity demonstrated that vitamin E enrichment caused an increase in enzyme activity. Analysis of cPLA2 protein by Western blot revealed that vitamin E caused an increase in enzyme protein. These data showed that the potentiation of arachidonic acid release and cPLA2, activity by vitamin E was mediated by the enhanced expression of cPLA2 protein.

Arachidonic Acid↗
PubMed1998

Inhibition of oxidant-induced lipid peroxidation in cultured renal tubular epithelial cells (LLC-PK1) by quercetin.

The protective effect of quercetin against oxidant-induced cell injury (hypoxanthine/xanthine oxidase system) was studied in the renal tubular epithelial cell line LLC-PK1. Pretreatment with quercetin provided protection from structural and functional cell damage in a concentration-dependent manner (10-100 microM). Comparison with structural variants revealed that the protective property of quercetin depends on the number of hydroxyl substituents in the B-ring, the presence of an extended C-ring chromophore, 3-D-planarity and lipophilicity, indicating that membrane affinity is essential for protection. The hypothesis that quercetin exerts its protective effects via inhibition of lipid peroxidation was further examined. Protection by quercetin was found when lipid peroxidation, assessed by the release of malondialdehyde, was initiated by H2O2 or by the combination of 1-chloro-2,4-dinitrobenzene and aminotriazole. In contrast, the bioflavonoid was not protective when oxidative cell damage was induced by menadione and occurred in the absence of lipid peroxidation. These data suggest that cytoprotective effects of quercetin are related to membrane affinity and may be explained by interruption of membrane lipid peroxidation rather than by intracellular scavenging of oxygen free radicals.

Animals↗
PubMed1998

A test statistic to detect errors in sib-pair relationships.

Several authors have proposed algorithms to detect Mendelian errors in human genetic linkage data. Most currently available methods use likelihood-based methods on multiplex family data to identify typing or pedigree errors. These algorithms cannot be applied in many sib-pair collections, because of lack of parental-genotype information. Nonetheless, misspecifying the relationships between individuals has serious consequences for sib-pair linkage studies: false relationships bias the statistics designed to identify linkage with disease phenotypes. To test the hypothesis that two individuals are sibs, we propose a test statistic based on the summation, over a large number of genetic markers, of the number of alleles shared identical by state by a pair of individuals, for each marker. The test statistic has an approximately normal distribution under the null hypothesis, and extreme negative values correspond to nonsib pairs. Power and significance studies show that the test statistic calculated by use of 50 unlinked markers has 96% power to detect half-sibs and has 100% power to detect unrelated individuals as not full-sib pairs, with a 5% false-positive rate. Furthermore, extreme positive values of the test statistic identify sibs as MZ twins.

Algorithms↗
PubMed1998

Human pathogenic virus-associated pseudolymphomas and lymphomas with primary cutaneous manifestation in humans and animals.

The etiologic role of viruses in cutaneous lymphoproliferative disorders is still controversial. In benign cutaneous pseudolymphomas of the human skin, human T-cell leukemia/lymphoma virus (HTLV) type I (HTLV-I), varicella zoster virus, Epstein-Barr virus (EBV), and human herpesvirus (HHV) 6 (HHV-6) are the viruses most often identified, whereas in malignant lymphoproliferation human immunodeficiency virus type 1 (HIV-1), HTLV-I/II, and EBV are more common. Coinfections with more than one virus species have occurred in a number of cases. HHV-8 in association with a lymphoproliferative lesion appears to be indicative of a malignant cutaneous lymphoma rather than of pseudolymphoma. Negative results are of no diagnostic value because of the relatively low number of virus-positive cases: a considerable proportion of studies (with a large number of subjects) have documented virus-negative findings. Perhaps with the exception of HIV-1, findings of viral infections seem to indicate secondary rather than primary infections. Reports on animal models associated with human pathogenic viruses are scarce.

Animals↗