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H Wagner

Publications and source records attributed to H Wagner.

At least 253 records · Page 14Linked to original sources
PubMed1995

Quantitative determination of element distributions in silicon based thin film solar cells using SNMS.

The determination of elemental distributions in thin film solar cells based on amorphous silicon using electron beam SNMS is possible by quantifying the measured ion intensities. The relative sensitivity factors (RSFs) for all elements measured have to be known. The RSFs have been determined experimentally using implantation and bulk standards with known concentrations of the interesting elements. The measured RSFs have been compared with calculated RSFs. The model used for the calculation of the RSFs takes into account the probability for electron impact ionization and the dwell time of the neutrals inside the postionization region. The comparison between measured and calculated RSF shows, that this model is capable to explain the RSFs for most elements. Differences between calculated and measured values can be explained by the formation of hydride and fluoride molecules (in case of H and F) and influences of the angular distribution of the sputtered neutrals in case of Al. The experimentally determined RSFs have been used for a quantification of depth profiles of the i-, buffer-, p- and front contact layers of a-Si solar cells.

Journal Article↗
PubMed1995

Acylated triterpene saponins from Silene jenisseensis.

From the roots of Silene jenisseensis a new trans-p-methoxycinnamoyl triterpene saponin has been isolated along with its cis-p-methoxycinnamoyl isomer as an inseparable mixture. Their structures were 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-[beta-D-glucopyranosyl-(1 --> 2)-alpha-L-rhamnopyranosyl- (1 --> 2)-beta-D-4-O-trans-p-methoxycinnamoyl-fucopyranosyl] quillaic acid and its cis-isomer, respectively. They did not show any activity in the in vitro chemoluminescence granulocytes assay, but exhibited only a weak inhibitory effect in the cyclooxygenase inhibition assay.

Acylation↗
PubMed1995

In vivo CTL induction with point-substituted ovalbumin peptides: immunogenicity correlates with peptide-induced MHC class I stability.

Class I molecules are conformationally sensitive to peptide binding, prolonging the complex's half-life on the surface of the cell. By making a series of H2-Kb anchor motif amino acid point substitutions in the ovalbumin 257-264 octamer, we were able to analyse subtle changes in peptide binding, Kb stabilization and in vivo immunogenicity. The cell line RMA-S was used to determine peptide-dependent Kb stabilization under equilibrium and non-equilibrium binding conditions. Sixteen conservative and non-conservative amino acid substitutions were made at positions 3, 5 or 8 of the peptide. At 37 degrees C, Kb stabilization was differentially affected by these substitutions, with several substitutions severely affecting Kb surface expression. When the substituted peptides were used as immunogens to prime cytotoxic T lymphocytes (CTL) in vivo, each peptide's ability to stabilize Kb directly correlated with the intensity of specific CTL activation. We conclude that peptide class I stabilization is an important influencing factor in determining cell surface steady-state expression of these peptides and thus the breadth of CTL recruitment. These concepts may relate the phenomenon of immunodominance to cell surface-presented peptide steady-state levels and may also aid in peptide vaccine design.

Amino Acid Sequence↗
PubMed1995

Phase II study with paclitaxel for the treatment of advanced inoperable non-small cell lung cancer.

Paclitaxel is a plant product isolated from the bark of the Western yew (Taxus brevifolia) that promotes the formation and stabilization of microtubules. This leads to growth arrest in the G2/M phase of the cell cycle. Paclitaxel has demonstrated significant antineoplastic activity in different tumor types, most notably in ovarian and breast carcinoma. In two Phase II trials (Eastern Cooperative Oncology Group [ECOG]/M.D. Anderson) in patients with previously untreated Stage IIIB-IV non-small cell lung cancer (NSCLC), response rates of 21% and 24% were reported. We are performing a Phase II trial investigating the efficacy of paclitaxel in patients with inoperable Stage IIIB-IV NSCLC. Forty-three patients were treated, 31 males and 12 females, with a median age of 59 years (range, 29-75), ECOG performance status 0-2, Stage IIIB 30%, Stage IV 70%. Patients were treated every 3 weeks with 225 mg/m2 as a 3-h infusion with standard premedication. Preliminary efficacy results from 37 patients include partial remissions in eight (21.6%) patients, no change in 22 (59.5%) and disease progression in seven (19%) patients. Eight patients are still receiving therapy. The hematologic toxicities (n = 43) were mild, and no World Health Organization (WHO) Grade 4 neutropenia was observed. Nonhematologic toxicities were Grade 1/2 polyneuropathy in 97.6%, Grade 1-3 myalgia/arthralgia in 76%, and Grade 1-3 nausea/vomiting in 18.6% of the patients. In conclusion, paclitaxel is an active single agent in this patient population. Mild hematologic toxicities were observed in the 3-h infusion setting (compared with 24-h infusion) and therapy was well tolerated.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Mechanistic evaluation of new plant-derived compounds that inhibit HIV-1 reverse transcriptase.

Swertifrancheside [1], a new flavonone-xanthone glucoside isolated from Swertia franchetiana, 1 beta-hydroxyaleuritolic acid 3-p-hydroxybenzoate [2], a triterpene isolated from the roots of Maprounea africana, and protolichesterinic acid [3], an aliphatic alpha-methylene-gamma-lactone isolated from the lichen Cetraria islandica, were found to be potent inhibitors of the DNA polymerase activity of human immunodeficiency virus-1 reverse transcriptase (HIV-1 RT), with 50% inhibitory doses (IC50 values) of 43, 3.7, and 24 microM, respectively. They were not cytotoxic with cultured mammalian cells. The kinetic mechanisms by which compounds 1-3 inhibited HIV-1 RT were studied as was their potential to inhibit other nucleic acid polymerases. Swertifrancheside [1] bound to DNA and was shown to be a competitive inhibitor with respect to template-primer, but a mixed-type competitive inhibitor with respect to TTP. On the other hand, 1 beta-hydroxyaleuritolic acid 3-p-hydroxybenzoate [2] and protolichesterinic acid [3] were mixed-type competitive inhibitors with respect to template-primer and noncompetitive inhibitors with respect to TTP. Therefore, the mechanism of action of 1 beta-hydroxyaleuritolic acid 3-p-hydroxybenzoate [2] and protolichesterinic acid [3] as HIV-1 RT inhibitors involves nonspecific binding to the enzyme at nonsubstrate binding sites, whereas swertifrancheside [1] inhibits enzyme activity by binding to the template-primer.

4-Butyrolactone↗
PubMed1995

Results of five randomized studies on the immunomodulatory activity of preparations of Echinacea.

This article describes and discusses five placebo-controlled randomized studies investigating the immunomodulatory activity of preparations containing extracts of Echinacea in healthy volunteers. A total of 134 (18 female and 116 male) healthy volunteers between 18 and 40 years of age were studied. Two studies tested intravenous homeopathic complex preparations containing Echinacea angustifolia D1 (study 1) and D4 (study 5). Two studies (2 and 3a) tested oral alcoholic extracts of roots of E. purpurea, one study an extract of E. pallida roots (study 3b), and one study an extract of E. purpurea herb (study 4). Test and placebo preparations were applied for four (study 5) or five (studies 1-4) consecutive days. The primary outcome measure for immunomodulatory activity was the relative phagocytic activity of polymorphonuclear neutrophil granulocytes (PNG), measured in studies 1 and 2 with a microscopic method and in studies 3, 4, and 5 with two different cytometric methods. The secondary outcome measure was the number of leukocytes in peripheral venous blood. Safety was assessed by a screening program of blood and other objective parameters as well as by documentation of all subjective side effects. In studies 1 and 2 the phagocytic activity of PNG was significantly enhanced compared with placebo [maximal stimulation 22.7% (95% confidence interval 17.5-27.9%) and 54.0% (8.4-99.6%), respectively], while in the other studies no significant effects were observed. Analysis of intragroup differences revealed significant changes in phagocytic activity during the observation periods in five test and three control groups. Leukocyte number was not influenced significantly in any study. Side effects due to the test preparations could not be detected. Our studies provide evidence for immunomodulatory activity of the homeopathic combination tested in study 1 and the E. purpureae radix extract tested in study 2. The negative results of the other three studies are difficult to interpret due to the different methods for measuring phagocytosis, the relevant changes in phagocytic activity within most placebo and treatment groups during the observation period, and the small sample sizes. Future studies should be performed on patients rather than healthy volunteers and use standardized or chemically defined monopreparations of Echinacea.

Adjuvants, Immunologic↗
PubMed1995

Superantigen-reactive T cells that display an anergic phenotype in vitro appear functional in vivo.

Clonal deletion and/or inactivation establishes tolerance to self antigens. Endogenous and exogenous (bacterial) superantigens, like the staphylococcal enterotoxins, induce ligand-specific clonal anergy in vivo and thus are believed to mirror aspects of post-thymic tolerance mechanisms in mature peripheral T cells. Here we analyzed the level of anergy of ligand-responsive V beta 8+ T cells from staphylococcal enterotoxin B (SEB)-primed mice in vivo and in vitro. Upon in vitro restimulation with SEB, CD4+V beta 8+ and CD8+V beta 8+ T cells failed to produce IL-2. However, functional IL-2 receptors were triggered, since supplementation with IL-2 induced clonal growth in virtually all CD4+V beta 8+ and CD8+V beta 8+ T cells as determined by limiting dilution analyses. Thus in vitro unresponsiveness of lymphocytes from SEB-primed mice reflects the inability of SEB-reactive V beta 8+ T cells to produce IL-2. Surprisingly, anergy as defined in vitro was at variance with that in vivo. Following further challenge with SEB, systemic and acute lymphokine production (including IL-2 and tumor necrosis factor) occurred with almost identical peak values and kinetics to primary in vivo responses, and D-galactosamine-sensitized mice succumbed to lethal shock. Polymerase chain reaction analyses revealed that CD4+V beta 8+ expressed IL-2-specific mRNA in vivo upon restimulation with SEB. While lymphokine production and expression of the IL-2 receptor was similar to the response to in vivo primary stimulation, only CD8+V beta 8+ T cells expanded clonally upon reintroduction of SEB in vivo. Hence primed V beta 8+ T cells challenged with SEB display in vitro anergy yet in vivo responsiveness, at least in part. We conclude that the state of anergy is reversible, dependent upon the quality of activation signals provided in in vivo rather than in in vitro culture conditions.

Animals↗
PubMed1995

Identification of H-2Kb binding and immunogenic peptides from human papilloma virus tumour antigens E6 and E7.

Peptides can be used to induce MHC class I restricted cytotoxic T cells (CTL) through in vivo immunization. This approach may enable the development of peptide vaccination schemes for immunization against viral infection in humans. Human papillomavirus (HPV) is one of a few viruses associated with human cancer and the development of an anti-cancer vaccine seems possible. As a model approach, we searched the E6 and E7 proteins of the human papillomavirus type 16 for possible murine MHC class I restricted peptide epitopes. We utilized the mouse H2-Kb peptide binding motif which consists of phenylalanine or tyrosine at position five and leucine at the carboxy-terminus with the modification that leucine could be replaced by other aliphatic but non-aromatic amino acids. Four peptide sequences from E6 and two from E7 were selected. These peptides were tested for their ability to bind and stabilize Kb and for their immunogenicity in vivo. It was shown that one peptide from E6, E6.1 (50-57), bound Kb, but was not able to prime mice in vivo. In contrast, the two selected E7 peptides E7.1 (21-28) and E7.2 (48-55) bound Kb and were immunogenic in vivo. The peptide induced CTL lysed syngeneic EL-4 cells transfected with the open reading frame of E7 but not vector only transfectants. This implies that both peptides were naturally processed and presented by Kb on the surface of target cells. MHC class I peptide binding motifs therefore appear to be an effective and useful tool to predict peptide epitopes of proteins associated with cancer.

Amino Acid Sequence↗
PubMed1995

Superantigens: the paradox of T-cell activation versus inactivation.

Superantigens are interesting for several reasons. They exhibit unusual T-cell activation characteristics, they allow to follow in vivo ligand-reactive T cells, they cause T-cell-mediated shock symptoms and they may be causally involved in certain human diseases. This review focuses on the paradox of T-cell activation versus T-cell inactivation as caused by bacterial superantigens in vivo. T-cell activation leads to the acute release of toxic concentrations of lymphokines including tumor necrosis factor alpha/beta, gamma-interferon, interleukin (IL)-2, IL-4 and IL-10. T-cell inactivation mirrors induction of anergy, T-cell receptor downregulation, and that of CD2, CD4 and CD8 cell surface molecules, as well as of apoptosis. Two waves of apoptosis cripple the T-cell repertoire of superantigen-reactive T cells, an immediate one being induced within 24 h and a late one occurring at days 3-4. In between, clonal expansion of anergic ligand-reactive T cells takes place.

Down-Regulation↗
PubMed1995

Screening, Early Detection, and Early Intervention Strategies for Lung Cancer.

Screening for lung cancer has been utilized for several decades without demonstrating overall survival benefit. However, recent advances in treatment of lung cancer, improvements in our biologic understanding of lung cancer development, and an increasing population of healthy ex-smokers provide cause for optimism. Several chemoprevention trials suggest that it may be possible to intervene in the oncologic process prior to the development of invasive malignancy, resulting in a delay or reversal of these changes.

Journal Article↗
PubMed1995

[Phase portraits of transfer systems--detection of nonlinear transmission properties between respiratory movements and heart rate fluctuations].

A new approach to the analysis of non-linear systems is proposed. It enables the reconstruction of the system state movement in a multi-dimensional phase space. The resulting phase portraits of the system behaviour were characterised quantitatively by estimating the correlation dimensions and prediction errors. This new approach was validated using simulated typical transfer systems. The measured respiratory movements and heart rate fluctuations of rabbits were employed for the first time to investigate the non-linear transfer properties between respiratory activity and heart rate in the system phase portraits. Significant non-linear transfer characteristics between respiratory movements and heart rate fluctuations were found--also during the awake phase--which have so far not been quantified.

Animals↗
PubMed1995

[Infected hip joint prosthesis. Viewpoints for 1-stage and 2-stage prosthesis exchange].

When treating an infected hip prosthesis, there are a number of medical, technical and biomechanical considerations. No ideal solution for all problems is available. In individual cases an optimal compromise must be found. The means for curing the infection and the one for maintaining hip stability can counteract each other. Basically, three options are available: removal of the prosthesis without replacement and one- or two-stage replacement. With all three options thorough surgical debridement is vitally important. The introduction of antibiotic cement and cementless titanium implants, together with very effective local antiseptics, has remarkably improved our treatment of this problem. Therefore, removal of infected prostheses without replacement is not as well accepted now as it has been in the past.

Anti-Bacterial Agents↗
PubMed1995

Sensitization of MHC class I-restricted T cells to exogenous proteins: evidence for an alternative class I-restricted antigen presentation pathway.

Immunization with exogenous proteins usually fails to immunize CD8+ T cells in vivo. Here we report that chicken ovalbumin (OVA) denatured by heat or sodium dodecyl sulphate (SDS) effectively induced CD8+ cytolytic T cells in vivo. The cytolytic T-lymphocyte (CTL) population generated recognized syngeneic target cells pulsed with the immunodominant OVA peptide (257-264) or transfected with the OVA protein-encoding gene. To analyse the mechanisms of how denatured OVA enters the class I-restricted pathway of antigen presentation, we took advantage of the fact that denatured OVA sensitizes target cells in vitro for lysis by OVA-specific CTL. We found that neither inhibition of protein synthesis (by cycloheximide) nor blocking of transport via the Golgi apparatus (by brefeldin A) interfered with the class I-restricted presentation of denatured OVA in vitro. In addition, transporter associated with antigen presentation (TAP)-dependent transport into the endoplasmic reticulum (ER) was not required for effective presentation, as TAP-deficient cells (RMA-S) could be sensitized effectively by denatured OVA for recognition by class I-restricted CTL. In contrast, class I-restricted presentation of denatured OVA was sensitive to lysosomotropic agents (NH4Cl, vinblastine and leupeptin), indicating that endosomal-like compartments are involved in the presentation of denatured OVA. Sensitization was inhibited at low temperature, yet took place in the presence of sucrose and in the absence of K+, indicating that denatured OVA enters the cell via fluid-phase endocytosis. Hence the results provide further evidence for an alternative class I-restricted pathway of antigen presentation for exogenous proteins. As that pathway seems to be effective in vivo, it offers a new and effective way of vaccination of CD8+ CTL.

Amino Acid Sequence↗
PubMed1995

Concurrent paclitaxel/cisplatin with thoracic radiation in patients with stage IIIA/B non-small cell carcinoma of the lung.

Nine patients with stage IIIB non-small cell lung cancer were entered into a phase II trial designed to determine the feasibility of giving a combination of paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) plus cisplatin concurrent with thoracic radiation. Paclitaxel was given as a 24-hour infusion (135 mg/m2) followed by cisplatin (75 mg/m2) every 4 weeks, for a total of four cycles. Thoracic radiation was given concurrently with the first two cycles of chemotherapy, for a total dose of 64.8 Gy over 6 weeks. Neutropenia and esophagitis were the most common toxicities, with 66% of patients experiencing grade 3 or 4 neutropenia and 55% experiencing grade 3 or 4 esophagitis. Grade 3 pulmonary toxicity developed in 33% of patients. All patients were able to receive the full dose of radiation, although half of the patients required some modification of the chemotherapy regimen. There was one complete response and four partial responses, yielding a 56% overall response rate. This study demonstrates that it is feasible to treat patients with stage IIIB non-small cell lung cancer with paclitaxel/cisplatin plus concurrent thoracic radiation, with a degree of toxicity comparable with that associated with a degree of toxicity comparable with that associated with other concurrent combined-modality regimens for this disease.

Aged↗
PubMed1995

Peptide engineering allows cytotoxic T-cell vaccination against human papilloma virus tumour antigen, E6.

Major histocompatibility complex (MHC) class I allele-specific binding motifs have proved useful in predicting cytotoxic T-cell epitopes from immunogenic proteins. In a search of the E6 protein from human papilloma virus type 16 utilizing the Kb binding motif, we discovered four potential binding peptides. One peptide, E6.1 (sequence 50-57, YDFAFRDL), was poor in its ability to stabilize empty Kb on RMA-S cells, with a t1/2 = 33 min versus 30 min for empty Kb. This peptide subsequently proved to be non-immunogenic upon mouse in vivo vaccination. It was hypothesized that an isoleucine for aspartate substitution at position 2 would improve Kb stabilization kinetics and therefore immunogenic potential. The engineered peptide E6.1 I2 increased the Kb t1/2 to 100 min and was immunogenic upon in vivo vaccination. Cytolytic T lymphocytes (CTL) raised with the E6.1 I2 peptide responded to cells pulsed with either the wild-type peptide or the engineered peptide, implying a blindness to the substitution. More striking, these CTL also lysed a syngeneic cell line transfected with the E6 gene, implying that the E6.1 peptide was processed and presented. These data demonstrate that subimmunogenic peptides can be engineered to improve binding kinetics, which in turn improves immunogenicity. Provided that poor binding peptides are processed, the induction threshold for CTL activation can be achieved with engineered peptides, thus allowing for the kill of wild-type target cells. This approach may prove relevant to the design of subunit vaccines to virally induced tumours.

Animals↗
PubMed1995

[Immunosuppression and infection].

The course of prolonged sepsis is characterized by an initial activation of the immune system followed by the transition into a state of immunosuppression. Accordingly, a series of immunosuppressive substances can be detected in the serum of septic patients. On the cellular level many important functions of the unspecific as well as the specific defense systems of the organism are inhibited. As a consequence, immunosuppression may be contributing to the fact, that patients suffering from prolonged sepsis hardly recover with a high risk to end in multiple organ dysfunction. However, increasing efforts to investigate this problem may result in therapeutic approaches which may help to improve the bad prognosis of sepsis.

Humans↗
PubMed1995

Interaction between gamma delta T cells and B cells regulating IgG production.

Despite profound knowledge about the molecular structure of the gamma delta T-cell receptor (TCR), the physiological function of gamma delta T cells remains enigmatic. Participation of these cells in complex immune reactions, however, is suggested by the appearance of gamma delta T cells in sites of infectious and autoimmune-induced inflammations. Only a few in vitro models of gamma delta T-cell stimulation have been established: besides a reactivity in the presence of microbial ligands, human gamma delta T cells proliferate upon in vitro challenge with cells from an allogeneic B-lymphoblastic cell line (B-LCL). We present data here demonstrating that this reactivity is not confined to allogenic B-LCL. Autologous B-LCL are also very strong stimulators for gamma delta T cells; more important, autologous B cells can stimulate gamma delta T cells after a period of mitogen-activation but not in a resting state. This activation seems to address a subgroup of gamma delta T cells, as the percentage of V delta 1+ cells is increased after stimulation. Activated gamma delta T cells, on the other hand, are able to exert an influence on B cells by inhibiting the secretion of IgG in coculture experiments. These data define a simple regulatory circle of B cells and gamma delta T cells in vitro and propose a model for gamma delta T-cell function which could explain many in vivo observations of gamma delta T-cell activation.

B-Lymphocytes↗