Search PubMed⌕ Search

Biomedical subjects

H Wagner

Publications and source records attributed to H Wagner.

At least 199 records · Page 11Linked to original sources
PubMed1997

The triterpenoid quinonemethide pristimerin inhibits induction of inducible nitric oxide synthase in murine macrophages.

Inducible nitric oxide synthase dependent production of nitric oxide (NO) plays an important role in inflammation. We investigated whether pristimerin ((20alpha)-3-hydroxy-2-oxo-24-nor-friedela-1(10),3,5,7-te traen-carboxylic acid-(29)-methylester), an antitumoral, antimicrobial as well as anti-inflammatory plant compound, has an effect on the inducible NO synthase system in lipopolysaccharide-activated RAW 264.7 macrophages. Pristimerin dose dependently (IC50: 0.2-0.3 microM) reduces nitrite accumulation, a parameter for NO synthesis, in supernatants of lipopolysaccharide-stimulated (1 microg/ml, 20 h) macrophages. This effect correlates with a reduced inducible NO synthase enzyme activity measured by conversion of [3H]L-arginine to [3H]L-citrulline and significantly lower levels of enzyme protein (Western blotting) in homogenates of cells cotreated with lipopolysaccharide and pristimerin (12 h). Northern blot analysis and polymerase chain reaction (PCR) showed decreased inducible NO synthase mRNA levels in activated macrophages exposed to pristimerin (4 h). Electrophoretic mobility shift assay (EMSA) demonstrated a markedly reduced binding activity of nuclear factor-kappa B (NFkappaB) in nuclear extracts of pristimerin-treated cells. These results suggest that pristimerin inhibits the induction of inducible NO synthase by a mechanism which involves inhibition of NFkappaB activation. This feature of pristimerin is likely to contribute to its anti-inflammatory activity.

Cell Line↗
PubMed1997

A rapid method for semiquantitative analysis of the human V beta-repertoire using TaqManR PCR.

Analysis of the V beta-repertoire of antigen-reactive T cell populations can be approached using either flow-cytometry or PCR-based techniques. While the former method requires a complete set of V beta-specific monoclonal antibodies (mAbs) and large cell numbers for analysis, the latter is both time-consuming and labour-intensive. To circumvent the drawbacks of both these methods we have employed the recently developed technique of TaqManR PCR to analyse the V beta-usage of human T cell populations. TaqManR PCR is based on the 5'-->3' nuclease activity of Taq polymerase. During PCR amplification an internal oligonucleotide probe, that is labelled with a fluorescent reporter and a quencher dye, is cleaved by Taq polymerase. After cleavage, quenching of the reporter dye is lost and reporter fluorescence can be detected with a fluorescence plate reader. Using one C beta-specific fluorogenic probe and a panel of V beta-specific primers, we show that fluorescence-detected amplification of TCR beta cDNA is V beta-specific and linear within a 2-3-log range of template concentration. The sensitivity of TaqManR PCR is comparable to conventional detection of PCR-products by agarose gel staining, while processing time is reduced. Furthermore, superantigen-induced skewing of the V beta-repertoire of human T cells is readily detected with this method. Thus TaqManR PCR is a reliable and fast method for semiquantitative analysis of the V beta-repertoire of human T cell populations.

Cells, Cultured↗
PubMed1997

Induction of acute inflammatory lung injury by staphylococcal enterotoxin B.

Superantigens stimulate T lymphocytes at high frequency by interacting with appropriate Vbeta segments of the TCR. Challenge of mice with bacterial superantigens such as staphylococcal enterotoxin B (SEB) induces the systemic release of cytokines resulting in septic shock and death of sensitized animals. Analysis of putative pathogenic mechanisms of T cell-dependent septic shock revealed that administration of SEB results in acute inflammatory lung injury characterized by a profound increase in vascular permeability. Injury was associated with marked leukocyte infiltration of the lung and induction of cell adhesion molecules including VCAM-1, ICAM-1, and P-selectin, but not E-selectin. Lung infiltrating leukocytes consisted of granulocytes, mononuclear phagocytes and NK cells with granulocytes representing the major fraction. Consistent with a role of neutrophils as cellular mediators of inflammatory organ injury, we demonstrate activation of circulating granulocytes in mice treated with SEB. When compared with granulocytes of control mice, peripheral blood granulocytes of SEB-treated mice were found to express increased levels of cell surface Mac-1, to down-regulate expression of L-selectin, and to respond with an increased production of toxic oxygen metabolites upon exposure to FMLP. Interestingly, TNF-alpha further enhanced FMLP-induced oxidant production by granulocytes from SEB-treated but not control mice, suggesting that the systemic response to SEB increases granulocyte sensitivity to TNF-alpha-mediated signals. Together, these results suggest that acute inflammatory lung injury may contribute to the pathogenesis of T cell-dependent lethal shock in mice challenged with bacterial superantigens and indicate common pathogenic mechanisms of lung injury induced by a large number of distinct inflammatory stimuli.

Acute Disease↗
PubMed1997

Superantigen and endotoxin synergize in the induction of lethal shock.

Endotoxin (lipopolysaccharide; LPS) and superantigens (exotoxins) have been identified as potent inducers of lethal shock. While endotoxin primarily interacts with CD14 receptors on macrophages, superantigens like the staphylococcal enterotoxin B (SEB) preferentially activate T cells. Both cell types are triggered to release pro-inflammatory cytokines that in turn induce lethal shock. We analyzed whether endotoxin and superantigen interact during the induction phase of lethal shock. We report that LPS and SEB operate synergistically. Lethal doses of both inducers were reduced 100-fold when given in combination. The induced serum levels of tumor necrosis factor, interleukin-6, and interferon-gamma (IFN-gamma) were elevated and remained high for a prolonged period. Moreover, synergistic action of LPS and SEB induced lethal toxic shock even without presensitization of mice with D-galactosamine (D-GalN). Opposed to D-GalN-pretreated mice, mice injected with LPS and SEB showed less liver damage, but rather apoptosis of epithelial cells in the bowel. Cyclosporin A and treatment with anti-IFN-gamma monoclonal antibody blocked the synergistic action of LPS and SEB, indicating that T cell-derived IFN-gamma is the mediator of the observed synergism. Concomitant injection of LPS and SEB had no influence on SEB-induced T cell deletion and anergy induction. Since Gram-positive and Gram-negative bacteria can be recovered from septic blood samples, the synergistic action of endotoxin and superantigens might be relevant during lethal septicemia.

Animals↗
PubMed1997

Macrophages sense pathogens via DNA motifs: induction of tumor necrosis factor-alpha-mediated shock.

Cell surface components of pathogens, such as lipopolysaccharide (LPS), are an important signal for receptor-mediated activation of immune cells. Here we demonstrate that DNA of gram-positive and gram-negative bacteria or certain synthetic oligonucleotides displaying unmethylated CpG-motifs can trigger macrophages in vitro to induce nuclear translocation of nuclear factor-kappa B, accumulate tumor necrosis factor (TNF)-alpha mRNA and release large amounts of TNF-alpha. In vivo these events culminate in acute cytokine-release syndrome which includes systemic but transient accumulation of TNF-alpha. D-Galactosamine (DGalN)-sensitized mice succumb to lethal toxic shock due to macrophage-derived TNF-alpha resulting in fulminant apoptosis of liver cells. LPS and a specific oligonucleotide synergized in vivo as measured by TNF-alpha-release, suggesting that macrophages integrate the respective signals. The ability of macrophages to discriminate and to respond to bacterial DNA with acute release of pro-inflammatory cytokines may point out an important and as yet unappreciated sensing mechanism for foreign DNA.

Animals↗
PubMed1997

CpG-containing synthetic oligonucleotides promote B and cytotoxic T cell responses to protein antigen: a new class of vaccine adjuvants.

Foreign DNA has been shown to impinge on immune cell function by an as yet unidentified mechanism. We and others have demonstrated that single-stranded (ss) DNA containing the motif CpG flanked by two 5' purines and two 3' pyrimidines are mitogenic for B cells and activate macrophages to release tumor necrosis factor-alpha, interferon-gamma, interleukin (IL)-6 or IL-12. Because of these pro-inflammatory responses we investigated if ssDNA would serve as a potential vaccine adjuvant. Here we show that CpG-containing oligonucleotides represent a powerful adjuvant for both humoral and cellular immune responses. When ssDNA was incorporated into inocula, specific antibody titers of the IgG2 isotype were enhanced by greater than 100-fold. Primary cytotoxic T lymphocyte responses generated to either unprocessed protein antigen or major histocompatibility complex class I-restricted peptide were exceedingly strong. Evidence is also provided that oligomers directly influenced T cell receptor-triggered T cell proliferation. Thus ssDNA oligomers may serve as inexpensive and safe vaccine adjuvants and, in addition, differential effects due to sequence may allow for directed responses.

Adjuvants, Immunologic↗
PubMed1997

Immunostimulatory DNA: sequence-dependent production of potentially harmful or useful cytokines.

Certain bacterial immunostimulatory (i.s.) DNA sequences containing unmethylated CpG motifs stimulate antigen-presenting cells (APC) to express a full complement of costimulatory molecules and to produce cytokines including interleukin (IL)-12 and tumor necrosis factor (TNF)-alpha. While IL-12 is key to their T helper cell (Th)1-promoting adjuvant activity, secretion of toxic levels of TNF-alpha is harmful in that it promotes toxic shock. Given the beneficial as well as harmful consequences of i.s. DNA, we investigated the possibility of identifying DNA sequences, i.e. CpG oligodeoxynucleotides (ODN) which differentially activate IL-12 versus TNF-alpha cytokine production in APC. Here, we describe an i.s. DNA sequence with these characteristics. While its potential to induce IL-12 is preserved, its ability to trigger TNF-alpha release is strongly curtailed both in vitro and in vivo. I.s. DNA could be segregated into lethal and non-lethal in a mouse toxic shock model. The non-toxic i.s. DNA was useful as an adjuvant, thus allowing cytotoxic T cell responses to the soluble protein ovalbumin and conferring a resistant Th 1 phenotype to BALB/c mice lethally infected with Leishmania major. This i.s. CpG motif may thus be prototypic for a useful immunostimulating DNA sequence that lacks harmful side effects.

Adjuvants, Immunologic↗
PubMed1997

Exactness of source analysis of biomagnetic signals of epileptiform spikes by the method of spatial filtering: a computer simulation.

On the basis of spatial covariance it is found that, by spatial filtering the localisation of a single dipole source, both parallel and perpendicular to the measurement plane (assuming a signal-noise ratio of 5:1), can be performed with an accuracy of < 0.5 mm. When the signal-noise ratio is increased to 30:1, the resolution of temporally independent current sources separated by 2 mm becomes practicable. This resolution study is carried out by means of a pair of unity current dipoles with the dipole distance as a varying source model parameter. The conclusions, drawn from the results of computer simulation and supported by statistical calculations, refer to the spherical model of the volume conductor of the brain.

Computer Simulation↗
PubMed1997

Jennisseensosides C and D, biologically active acylated triterpene saponins from Silene jenisseensis.

We previously reported the isolation and structure elucidation of a new trans-p-methoxycinnamoyl triterpene-saponin along with its cis-p-methoxycinnamoyl isomer as an inseparable mixture from the roots of Silene jenisseensis. In a continuing study on this plant, two additional new acylated triterpene-saponins were obtained as an inseparable mixture. Their structures have been established by chemical means and spectroscopic methods including 1D and 2D homonuclear and heteronuclear correlation NMR spectroscopy as 3-O-[beta-D-galactopyranosyl-(1-->2)-beta-D-glucuronopyranosyl]-28 -O-[{alpha-L-rhamnopyranosyl-(1-->2)}-{4-O-trans-p-methoxycinnamoyl++ +}-beta-D-fucopyranosyl] quillaic acid and its cis-isomer, respectively. They showed a significant enhancement of the granulocyte phagocytosis in vitro.

Carbohydrate Conformation↗
PubMed1997

Principles of acoustic motion detection in animals and man.

Motion provides one of the most important cues for survival, because it helps to break the camouflage of a predator or a prey and because it allows predictions about the future path of an object. Recent data on the processing of acoustic motion have yielded some astonishing findings, suggesting that the psychophysical, neurological and neurophysiological mechanisms underlying the detection and representation of acoustic motion are quite similar to those underlying the detection and representation in other modalities, especially in vision. A further comparison of these similarities and differences with respect to the different environmental constraints posed for the different modalities may help in understanding general problems associated with motion computations.

Animals↗
PubMed1997

Thoracic irradiation of limited small cell lung cancer: have we defined optimal dose, time, and fractionation?

There is a general agreement that patients with limited small cell lung cancer (L-SCLC) are better treated with a combination of thoracic radiation therapy (TRT) and systemic chemotherapy (CT) than with either modality alone. There is little agreement, however, and few data from prospective trials, to define optimal ways of combining these modalities. This article will review available data on radiation dose, timing, fractionation, and volume issues in an attempt to develop standards for current practice and suggest appropriate questions for future prospective clinical trials.

Carcinoma, Small Cell↗
PubMed1997

Monitoring brain tumor response to therapy using MRI segmentation.

The performance evaluation of a semi-supervised fuzzy c-means (SFCM) clustering method for monitoring brain tumor volume changes during the course of routine clinical radiation-therapeutic and chemo-therapeutic regimens is presented. The tumor volume determined using the SFCM method was compared with the volume estimates obtained using three other methods: (a) a k nearest neighbor (kNN) classifier, b) a grey level thresholding and seed growing (ISG-SG) method and c) a manual pixel labeling (GT) method for ground truth estimation. The SFCM and kNN methods are applied to the multispectral, contrast enhanced T1, proton density, and T2 weighted, magnetic resonance images (MRI) whereas the ISG-SG and GT methods are applied only to the contrast enhanced T1 weighted image. Estimations of tumor volume were made on eight patient cases with follow-up MRI scans performed over a 32 week interval during treatment. The tumor cases studied include one meningioma, two brain metastases and five gliomas. Comparisons with manually labeled ground truth estimations showed that there is a limited agreement between the segmentation methods for absolute tumor volume measurements when using images of patients after treatment. The average intraobserver reproducibility for the SFCM, kNN and ISG-SG methods was found to be 5.8%, 6.6% and 8.9%, respectively. The average of the interobserver reproducibility of these methods was found to be 5.5%, 6.5% and 11.4%, respectively. For the measurement of relative change of tumor volume as required for the response assessment, the multi-spectral methods kNN and SFCM are therefore preferred over the seedgrowing method.

Adult↗
PubMed1997

Listeriosis in p47(phox-/-) and TRp55-/- mice: protection despite absence of ROI and susceptibility despite presence of RNI.

The significance of host defense mechanisms in primary listeriosis in vivo is incompletely understood. Here, we show that tumor necrosis factor receptor p55-/- (TRp55-/-) mice are susceptible to Listeria monocytogenes infection in the presence of leukocyte recruitment, inflammatory cytokine production (including IFNgamma), nitric oxide synthesis, and oxidative burst formation. Mice deficient for oxidative burst (p47[phox-/-] mice) are relatively resistant to listeriosis. Despite activation of these antibacterial effector systems, TRp55-/- phagocytes in vivo are incapable of confining and eradicating L. monocytogenes inside phagolysosomes. Bone marrow chimeras reveal that for eradication of L. monocytogenes, TRp55 is crucially required only on cells from hematopoietic origin. Unexpectedly, prior to death, exocrine pancreatic cells undergo apoptosis in TRp55-/- mice. Collectively, these data demonstrate that in vivo, TRp55 initiates a protective, listericidal mechanism in phagocytes that differs from nitric oxide production and oxidative burst formation and that uncontrolled listeriosis results in necrotizing pancreatitis in TRp55-/- mice.

Animals↗
PubMed1997

Distinct mechanisms of immunosuppression as a consequence of major surgery.

Altered host defense mechanisms after major surgery or trauma are considered important for the development of infectious complications and sepsis. In the present study, we demonstrate that major surgery results in a severe defect of T-lymphocyte proliferation and cytokine secretion in response to coligation of the antigen receptor complex and CD28. During the early postoperative course, reduced cytokine secretion was observed for interleukin-2 (IL-2), gamma interferon, and tumor necrosis factor alpha, which are associated with the Th1 phenotype of helper T lymphocytes, and for IL-4, the index cytokine of Th2 cells. During the late postoperative course, T-cell cytokine secretion increased to normal levels. Production of the anti-inflammatory cytokine IL-10 was altered, with different kinetics being selectively elevated during the late postoperative course. In contrast, the capacity of peripheral blood monocytes to present bacterial superantigens and to stimulate T-cell proliferation was normal or enhanced after surgery despite a significant loss of cell surface HLA-DR molecules. Thus, the level of major histocompatibility complex class II protein expression does not appear to predict the antigen-presenting capacity of monocytes obtained from surgical patients with uneventful postoperative recovery. Secretion of IL-1beta and IL-10 by endotoxin-stimulated peripheral blood monocytes was increased at different time points after surgery. Major surgery therefore results in a distinct pattern of immune defects with a predominant defect in the T-cell response to T-cell receptor- and CD28 coreceptor-mediated signals rather than an impaired monocyte antigen-presenting capacity. Suppression of T-cell effector functions during the early phase of the postoperative course may define a state of impaired defense against pathogens and increased susceptibility to infection and septic complications.

Aged↗
PubMed1997

Effects of inhaled nitric oxide on gas exchange in lungs with shunt or poorly ventilated areas.

Inhaled nitric oxide (NO) is a selective pulmonary vasodilator with beneficial effects on some lung diseases, yet conflicting results, particularly in chronic obstructive pulmonary disease, have been reported. We hypothesized that although inhaled NO would improve gas exchange in the presence of shunt (by increasing blood flow to normal areas), it could worsen gas exchange when areas of low ventilation-perfusion (VA/Q) ratio were present since these areas could be preferentially vasodilated by NO. We examined how approximately 80 ppm inhaled NO altered pulmonary gas exchange in anesthetized ventilated dogs with the following: (1) normal lungs (n = 8), (2) shunt (n = 9, 24.7% shunt) produced by complete obstruction of one lobar bronchus, and (3) VA/Q inequality (n = 8) created by partial obstruction of one lobar bronchus resulting in a bimodal VA/Q distribution with 13% perfusion of low VA/Q areas (0.005 < VA/Q < 0.1) without shunt. Inhaled No significantly reduced pulmonary arterial (p < 0.001) and wedge pressures (p < 0.01) and pulmonary vascular resistance (p < 0.01) without changing cardiac output in each group. In normal lungs, NO did not alter PaO2 or VA/Q inequality. However, with complete obstruction, shunt fell slightly (p < 0.001) with NO. In lungs with VA/Q inequality, NO variably affected VA/Q matching, which was improved in some dogs and worsened in others. In these lungs, changes in pulmonary vascular resistance of the abnormal area of the lung were negatively correlated with changes in VA/Q dispersion (logSDQ) (R = -0.85, p < 0.01) and positively correlated with PaO2 (R = 0.79, p < 0.05). We conclude that NO has net effects on pulmonary gas exchange, depending on the underlying lung pathology consistent with competing vasodilatory effects on the normal and abnormal areas that receive the gas.

Administration, Inhalation↗
PubMed1997

Prophylactic cranial irradiation for patients with small cell lung cancer. An enduring controversy.

Small cell lung cancer (SCLC) is a systemic disease that usually presents with locally bulky disease in the lung and mediastinal nodes, with either subclinical (limited stage) or detectable (extensive stage) extrathoracic metastases. Treatment with local modalities alone leads almost invariably to systemic relapse, and treatment with only systemic therapy usually results in recurrence at sites of initially demonstrated disease. Although prophylactic cranial radiation is far from an ideal solution to the problem of CNS metastases in patients with SCLC, it presently seems preferable to the alternative of observation and generally ineffective palliative treatment at time of relapse in the CNS.

Antineoplastic Agents↗