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Biomedical subjects

H Wagner

Publications and source records attributed to H Wagner.

At least 217 records · Page 12Linked to original sources
PubMed1997

Effect of lobaric acid on cysteinyl-leukotriene formation and contractile activity of guinea pig taenia coli.

Lobaric acid, a constituent of the lichen Stereocaulon alpinum, was investigated for effects on the smooth muscle taenia coli from guinea pigs. Inhibitory effects of lobaric acid on spontaneous contractile activity and on contractile activity stimulated by ionophore A23187 were studied. In addition, the activity of lobaric acid on ionophore-induced generation of cysteinyl-leukotrienes in taenia coli was determined by enzyme immunoassay. Lobaric acid significantly reduced spontaneous contractile activity of the muscle and inhibited contractions caused by ionophore A23187 with an effective dose of 5.8 microM. Increased contractility caused by leukotriene D4 was not influenced by lobaric acid. Lobaric acid inhibited the formation of cysteinyl-leukotrienes as determined by enzyme immunoassay with an effective dose of 5.5 microM.

Animals↗
PubMed1997

Radiation therapy in the management of patients with unresectable stage IIIA and IIIB non-small cell lung cancer.

Treatment of patients with unresectable stage IIIA and IIIB non-small cell lung cancer with conventional radiation therapy has resulted in poor local control, a high rate of systemic failure, and 5-year survival of less than 10%. Recent modification in radiation treatment planning, dose delivery, and fractionization has demonstrated significantly improved median and 2-year survival, comparable in some trials to that achieved with induction chemotherapy followed by radiation. Current trials focus on combining systemic therapy with dose-intense radiation therapy to improve with local and systemic control.

Carcinoma, Non-Small-Cell Lung↗
PubMed1997

Combined-modality therapy of locally advanced non-small-cell lung cancer.

Treatment of patients with unresectable stage IIIA and IIIB non-small-cell lung cancer with conventionally-fractionated radiation therapy (i.e., total doses of 50 to 60 Gy, using one fraction per day), which was standard practice in the 1970s and early 1980s, resulted in good short-term palliation but few long-term survivors. Local control was poor, and the majority of patients also rapidly developed symptomatic metastatic disease outside the chest. In the past 15 years, a number of approaches to improve this situation have been defined in prospective clinical trials. They include radiation therapy with altered fractionation schemes that allow either higher overall doses or shortened treatment times, the use of systemic chemotherapy to address microscopic metastatic disease, and the use of a variety of agents, some but not all with intrinsic cytotoxic activity, to act as radiation sensitizers. These strategies have resulted in modest but significant improvements in local and systemic disease control, but at a cost of increased toxicity, including myelosuppression, esophagitis, and pneumonitis. Further advances in treatment will require better (i.e., more active) cytotoxic agents and better ways of limiting radiation effects to the target volume of tumor.

Carcinoma, Non-Small-Cell Lung↗
PubMed1996

A neuronal learning rule for sub-millisecond temporal coding.

A paradox that exists in auditory and electrosensory neural systems is that they encode behaviorally relevant signals in the range of a few microseconds with neurons that are at least one order of magnitude slower. The importance of temporal coding in neural information processing is not clear yet. A central question is whether neuronal firing can be more precise than the time constants of the neuronal processes involved. Here we address this problem using the auditory system of the barn owl as an example. We present a modelling study based on computer simulations of a neuron in the laminar nucleus. Three observations explain the paradox. First, spiking of an 'integrate-and-fire' neuron driven by excitatory postsynaptic potentials with a width at half-maximum height of 250 micros, has an accuracy of 25 micros if the presynaptic signals arrive coherently. Second, the necessary degree of coherence in the signal arrival times can be attained during ontogenetic development by virtue of an unsupervised hebbian learning rule. Learning selects connections with matching delays from a broad distribution of axons with random delays. Third, the learning rule also selects the correct delays from two independent groups of inputs, for example, from the left and right ear.

Animals↗
PubMed1996

Initial results of a phase II trial of high dose radiation therapy, 5-fluorouracil, and cisplatin for patients with anal cancer (E4292): an Eastern Cooperative Oncology Group study.

PURPOSE: A prospective clinical trial was performed to assess the response and toxicity associated with the use of high dose radiation therapy, 5-fluorouracil, and cisplatin in patients with anal cancer. METHODS AND MATERIALS: Patients with anal cancer without distant metastasis were eligible for this study. Radiation therapy consisted of 59.4 Gy in 33 fractions; a 2 week break in treatment was taken after 36 Gy had been given. A treatment of 5-fluorouracil, 1,000 mg/m2 per day intravenously, was given for the first 4 days of radiation therapy, and cisplatin, 75 mg/m2 intravenously, was given on day 1 of radiation therapy. A second course of 5-fluorouracil and cisplatin was given after 36 Gy of radiation, when the radiation therapy was resumed. RESULTS: Nineteen patients entered this study and received treatment. Thirteen (68%) had a complete response, 5 (26%) had a partial response, and 1 (5%) had stable disease. The patient with stable disease and one of the patients with a partial response had complete disappearance of tumor more than 8 weeks after completion of radiation therapy. Fifteen patients had toxicity of Grade 3 or higher: the worst toxicity was Grade 3 in eight patients, Grade 4 in six patients, and Grade 5 in one patient. The most common form of toxicity of Grade 3 or higher was hematologic. The one lethal toxicity was due to pseudomembranous colitis, which was a complication of antibiotic therapy for a urinary tract infection. CONCLUSION: Radiation therapy, cisplatin, and 5-fluorouracil resulted in an overall response rate of 95%. Significant toxicity occurred, an indication that this regimen is near the maximal tolerated dose. A Phase III clinical trial is planned in which radiation therapy, cisplatin, and 5-fluorouracil will be used as an experimental arm.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

Asp333, Asp495, and His523 form the catalytic triad of rat soluble epoxide hydrolase.

On the basis of the sequence similarity between mammalian epoxide hydrolases and bacterial haloalkane dehalogenase reported earlier (Arand, M., Grant, D. F., Beetham, J. K., Friedberg, T., Oesch, F., and Hammock, B. D. (1994) FEBS Lett. 338, 251-256; Beetham, J. K., Grant, D., Arand, M., Garbarino, J., Kiyosue, T., Pinot, F., Oesch, F., Belknap, W. R., Shinozaki, K., and hammock, B. D. (1995) DNA Cell. Biol. 14, 61-71) we selected candidate amino acid residues for the putative catalytic triad of the rat soluble epoxide hydrolase. The predicted amino acid residues were exchanged by site-directed mutagenesis of the epoxide hydrolase cDNA, followed by the expression of the respective mutant enzymes in Escherichia coli. A total of 25 different mutants were analyzed for their epoxide hydrolase activity toward the model substrate trans-stilbene oxide. In case of impaired catalytic activity of a given mutant, the structural integrity of the recombinant enzyme protein was assessed either by its ability to covalently bind the substrate trans-stilbene oxide or by affinity purification on benzyl thio-Sepharose, using the soluble epoxide hydrolase-specific competitive inhibitor 4-fluorochalcone oxide to release the bound enzyme from the affinity matrix. Of the mutants under investigation, only those with changes in the positions Asp333, Asp495, and His523 were completely inactive toward the model substrate trans-stilbene oxide while retaining the proper protein fold. These amino acids were exactly those previously predicted by sequence alignment. Exchange of the amino acid residues flanking the catalytic nucleophile Asp333 significantly changed the kinetic properties of the enzyme. Mutation of His332 to Gln had no apparent effect on the Km but led to a heavily reduced Vmax (5% that of the wild type) of the mutant enzyme, while the exchange of Trp334 against Phe strongly increased the Km (7-fold) and also moderately enhanced the Vmax (2-fold) of the corresponding mutant. Mutation of Trp540 apparently had a strong effect on the protein conformation.

Amino Acid Sequence↗
PubMed1996

Mechanisms of peripheral T cell deletion: anergized T cells are Fas resistant but undergo proliferation-associated apoptosis.

The complementary receptor pair Fas ligand: Fas controls apoptosis during activation-induced cell death (AICD) of peripheral T cells sensitized for the Fas signal pathway by interleukin-2 (IL-2). In the present study, we used the bacterial superantigen staphylococcal enterotoxin B (SEB) to anergize ligand-reactive peripheral T cells in wild-type and Fas-defective lpr mice. In a second step, we investigated whether apoptosis in anergized and thus operationally IL-2-defective peripheral T cells is triggered via the Fas signal pathway. We report here that SEB-driven anergy induction and deletion of anergized peripheral V beta 8+ T cells is similar in wild-type and healthy C3H/lpr mice. In monitoring SEB-driven V beta 8+ T cell apoptosis in situ, we observe in both wild-type and lpr mice an intimate association between proliferation and apoptosis of anergized V beta 8+ T cells. We further show that V beta 8+ T cells activated in vitro from wild-type mice express a Fas-sensitive phenotype determined by Fas cross-linking which causes apoptosis. In contrast, V beta 8+ T cells anergized in vivo from wild-type mice are Fas resistant. As expected, T cells from lpr mice activated in vitro or anergized in vivo are Fas resistant. Taken together, these data indicate that both in wild-type and Fas-defective C3H/lpr mice, anergized T cells become deleted via a Fas-independent, proliferation-associated apoptosis signal pathway.

Animals↗
PubMed1996

Cryopreservation of porcine hepatocyte cultures.

Cryopreservation of freshly isolated hepatocytes is regarded the standard procedure for long term storage of liver cells. However, a dramatic loss in cell number, viability, and differentiated cell function is usually inevitable, and, upon thawing, hepatocytes do not attach well in culture. Freezing of hepatocyte cultures has already been shown to reduce these hazardous effects, probably due to the beneficial impact of a repair phase that allows the cells to restore their membranes during the first days of culture prior to and after freezing. We have compared the performance of porcine hepatocytes from slaughterhouse organs that were frozen at day 3 of immobilizing gel culture and stored at -80 degrees C for increasing time intervals up to 30 days (three groups; n = 3 each). Control groups consisted of batch identical hepatocyte cultures, either frozen at a fixed cooling rate (-1 degrees C/min; n = 3), subjected to rapid freezing (-10 degrees C/min; n = 3) or left without any freezing (n = 4). Upon thawing, light and electron microscopic studies revealed a cell survival rate of 70.3 +/- 10.5% (mean +/- SD; n = 9) in hepatocyte cultures after adjusted rate-controlled freezing. In these groups, the length of storage time did not influence results. Functional parameters, like albumin secretion values and ethoxycoumarin deethylase activity (cytochrome P450-IA1) were comparable to non-frozen cultures after a recovery time of 48 h post-thaw. Fixed cooling rates at -1 degrees C and -10 degrees C, respectively, showed a greater reduced viability (35.4 +/- 7.4%; 9. 87 +/- 2.8%) and a severely impaired post-thaw functional performance of cultures. Cryopreservation of hepatocyte cultures could provide a practical means of establishing a bank of hepatocyte cultures. This could be extremely useful for the development of a hybrid artificial liver device, and it might support repeated investigations on batch-controlled hepatocyte cultures, especially with respect to human cells.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1996

Integration of foreign sequences into the tobacco plastome via polyethylene glycol-mediated protoplast transformation.

A new vector, pFaadAII, for transformation of plastids of Nicotiana tabacum L. has been developed. It harbours a chimeric gene consisting of the aadA coding region from Escherichia coli, the 16S rDNA promoter from tobacco combined with a synthetic ribosome-binding site, a 500-bp fragment containing the 3' untranslated transcript region (UTR) of the Chlamydomonas rbcL gene and 3.75-kb (5') and 0.95-kb (3') tobacco plastome sequences allowing for targeting the foreign sequences to the intergenic region between the rpl32 and trnL genes of the tobacco plastome. The vector thus targets foreign sequences to the small single-copy region of the plastome, which has so far not been modified by transformation. Leaf protoplasts of Nicotiana tabacum L. were treated with polyethylene glycol (PEG) in the presence of the vector. The protocol for PEG treatment aiming at plastome transformation was optimized. Cell lines were cultured in the presence of spectinomycin and streptomycin using a novel and efficient protoplast culture and selection system. Regenerants were characterized by polymerase chain reaction (PCR) analysis, Southern hybridization and reciprocal crossing. The transformation procedure is described in detail and parameters influencing its efficiency are presented. Special effort is placed on analyzing suitable selection conditions. Only a proportion of the cell lines with a resistant phenotype could be confirmed by molecular analysis and/or reciprocal crossings to represent plastome transformants. Integration of the plastome specific aadA cassette into the nuclear genome accounted for a fraction of the resistant cell lines. Still, as many as 20-40 plastome transformants can be expected from the treatment of 10(6) protoplasts. Therefore, the improved protocol for PEG-mediated plastome transformation in combination with the new aadA-vector supplies a simple, reproducible and cost-efficient alternative to the biolistic procedure.

Base Sequence↗
PubMed1996

HLA-A2-restricted peripheral blood cytolytic T lymphocyte response to HPV type 16 proteins E6 and E7 from patients with neoplastic cervical lesions.

The DNA from human papillomavirus (HPV) can be detected in 90% of cervical carcinomas. To address whether patients infected with HPV can mount efficient T cell responses to this pathogen we examined the cytotoxic T lymphocyte (CTL) response of peripheral blood mononuclear cells (PBMC) from patients with abnormal genital epithelial cells. PBMC from 11 HLA-A2+ patients were stimulated with CaSki, a cervical carcinoma cell line that is HPV 16+ and HLA-A2+. The CTL were screened for reactivity to the cervical carcinoma cell line C33A (HPV-, HLA-A2+) transfected with the HPV 16 E6 or E7 genes or the plasmid without insert. The CTL of 1 patient showed particularly strong CaSki and HPV E6 or E7 protein-specific cytotoxicity in a HLA-A2+-restricted fashion. In contrast, these CTL lysed neither a vector-only transfectant, the natural killer cell (NK) target, K562 nor the lymphokine-activated killer cell (LAK) target, Daudi. HLA-A2 restriction was demonstrated by the lack of recognition of a HLA-A2- CaSki cell line developed in our laboratory. The CTL line was cloned and 99 clones were harvested and screened; 51 clones lysed CaSki, of which 17 did not lyse the A2- CaSki. Of these HLA-A2- restricted clones, 8 did not lyse C33A transfectants, 6 lysed all C33A transfectants, 3 lysed C33A-E7 only and none lysed C33A-E6 only. These data imply that, within the bulk CTL line, HLA-A2-restricted recognition of antigens was restricted to CaSki antigens, antigens common to cervical carcinoma (CaSki plus C33A), or HPV-16-E7-derived antigen on the clonal level. The E7-restricted clones were negative for recognition of known HLA-A2-binding peptides from E7.

Base Sequence↗
PubMed1996

Nevadensin glycosides from Lysionotus pauciflorus.

Two new flavone glucosides, nevadensin 5-O-beta-D-glucoside and nevadensin 5-O-beta-D-glucosyl(1-->6)beta-D-glucoside, have been isolated from the aerial parts of Lysionotus pauciflorus. The structures have been determined by means of UV, mass spectral and one- and two-dimensional 1H and 13C NMR techniques.

Animals↗
PubMed1996

Neural encoding of binocular disparity: energy models, position shifts and phase shifts.

Neurophysiological data support two models for the disparity selectivity of binocular simple and complex cells in primary visual cortex. These involve binocular combinations of monocular receptive fields that are shifted in retinal position (the position-shift model) or in phase (the phase-shift model) between the two eyes. This article presents a formal description and analysis of a binocular energy model with these forms of disparity selectivity. We propose how one might measure the relative contributions of phase and position shifts in simple and complex cells. The analysis also reveals ambiguities in disparity encoding that are inherent in these model neurons, suggesting a need for a second stage of processing. We propose that linear pooling of the binocular responses across orientations and scales (spatial frequency) is capable of producing an unambiguous representation of disparity.

Depth Perception↗
PubMed1996

Marchantins and related polyphenols from liverwort: physico-chemical studies of their radical-scavenging properties.

Structurally unique macrocyclic phenols from liverwort, i.e., marchantins and related substances, were studied for their antioxidative potential using pulse-radiolytic and EPR-spectroscopic techniques. The generally diffusion-controlled rate constants for scavenging of azide radicals as a model electrophilic species and the sufficiently slow bimolecular decay confirm their antioxidative potential. Transient spectra after pulse radiolysis and the EPR spectra both demonstrate the internal strain of the macrocyclic ring. One compound, Perrottetin D, furthermore gave proof to the hitherto only kinetically verifyable superior radical-scavenging capability of the aroxyl radical derived from a phenolic antioxidant.

Catechols↗
PubMed1996

Glucocorticoids decrease the production of parathyroid hormone-related protein in vitro but not in vivo in the Walker carcinosarcoma 256 rat model.

In 50-90% of cases, humoral hypercalcemia of malignancy (HHM) is due to tumor secretion of parathyroid hormone-related protein (PTHrP). Glucocorticoids are sometimes used as calcium lowering agents and there are in vitro results showing that glucocorticoids diminish PTHrP production. In this study we tested whether the serum-calcium-lowering effect of glucocorticoids is due to decreased PTHrP production by the tumor. As an animal and cell culture model we used the Walker carcinosarcoma (WCS) 256, a rat mammary carcinoma cell line producing PTHrP. In vitro, dexamethasone caused a dose-dependent inhibition of PTHrP production, whereby already 1-5 nmol/L revealed a significant decrease by WCS 256 cells. In contrast to these in vitro results, in WCS 256 tumor-bearing rats, dexamethasone (4 mg/kg body weight on day 4, and 1 mg/kg body weight from day 5 until day 7 after WCS transplantation; circulating dexamethasone levels > 20 nmol/L) did not decrease PTHrP production, PTHrP secretion, serum calcium, or tumor weight in vivo. We conclude that, in this PTHrP-mediated model of humoral hypercalcemia of malignancy, glucocorticoids do not decrease PTHrP production and secretion in vivo and do not show a calcium-lowering effect.

Analysis of Variance↗
PubMed1996

Preliminary results of uncemented metal on metal stemmed and resurfacing hip replacement arthroplasty.

Seventy uncemented stemmed total hip replacements and 35 uncemented surface replacements with all metal Metasul articulating surfaces were followed up in a prospective study. There was no evidence that this metal on metal articulation causes new problems or complications that were not known already from other polyethylene-aluminum oxide ceramic articulating combinations. The results of 64 of 70 patients could be assessed as excellent and good. When tissue samples obtained during 2 reoperations for ectopic ossification were examined histologically, there was no light microscopic evidence of metal particles. In these cases, aseptic loosening seemed to be due to the lack of initial fixation with the original femoral component design, and was not related to the use of the Metasul bearing. The metal on metal articulation reduces the production of particles considerably according to experience to date. It is therefore hoped that foreign body reactions due to wear particles will be significantly reduced. The results support the continued investigation of metal on metal joint replacements for younger, active patients.

Adolescent↗
PubMed1996

Rapid clearance of the bacterial superantigen staphylococcal enterotoxin B in vivo.

Following bolus injection of the superantigen Staphylococcus enterotoxin B (SEB) into mice, ligand-reactive T cells are triggered to release toxic amounts of lymphokines. Subsequently, within 6 to 10 h ligand-reactive Vbeta8+ T cells become anergic and clonally expand and thereafter are deleted via apoptosis. Since the binding affinities of SEB to major histocompatibility complex (MHC) class II molecules are as low as 1.7 microM, the concentration of SEB in the fluid phase dictates the presentation via MHC class II molecules. Here, we study the pharmacokinetics of SEB in vivo and correlate pharmacokinetics with immunogenicity. We describe here how after a bolus injection of SEB, the superantigen becomes systemically distributed, with peak levels within 5 to 30 min in blood and in lymph nodes. Clearance occurs within 10 to 24 h, with the kidneys being a major route. To induce T-cell activation in vivo, SEB must be present in concentrations above 10(-4) microg/ml. These concentrations exist for only 15 h. Manifestation of functional outcomes such as anergy, clonal expansion, and clonal deletion begins after 24 h. We conclude that the SEB model system can be used to separate the phase of T-cell receptor ligation from the phase of manifestation of functional outcomes.

Animals↗
PubMed1996

Characterization of clinical isolates of Escherichia coli showing high levels of fluoroquinolone resistance.

During the years 1992 to 1994, an increase in fluoroquinolone-resistant Escherichia coli was observed at the Medical Center of the Technical University in Munich, Germany. Nineteen strains were collected and were thus available for further analysis. Pulsed-field gel electrophoresis showed clonal diversity in all but two strains. The majority of the patients from whom the strains were isolated had been previously treated with fluoroquinolones. Quinolone resistance was associated with mutations of the quinolone resistance-determining region of the gyrA gene in all cases. Direct sequencing of gyrA PCR amplification products revealed a mutation in codon 83 of the gyrA gene. In some instances the Ser-83-->Leu mutation was accompanied by an Asp-87-->Asn or Asp-87-->Gly mutation. Furthermore, the strains exhibited two different genotypes: in almost half of the fluoroquinolone-resistant E. coli strains as well as in the fluoroquinolone-susceptible E. coli reference strains ATCC 25922 and 35218, silent mutations were detected at bases 255, 273, 300, and 333. Although fluoroquinolones solved major problems in antimicrobial chemotherapy, in certain departments of our hospital the number of resistant E. coli isolates has become so high that susceptibility to fluoroquinolones can no longer be taken for granted.

Anti-Infective Agents↗