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Search Results: 1 - 10 of 32582 matches for " Peter Koehler "
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Electrochemical Immunosensors for the Diagnosis of Celiac Disease  [PDF]
Katharina Anne Scherf, Peter Koehler, Herbert Wieser
Advances in Chemical Engineering and Science (ACES) , 2015, DOI: 10.4236/aces.2015.51009
Abstract: Celiac disease is a permanent intolerance to gluten proteins of wheat, rye, barley, and oats in genetically susceptible individuals. The clinical picture is characterized by inflammation and damage of the small intestinal mucosa and malabsorption of essential nutrients. Therapeutically, a lifelong strict gluten-free diet is necessary. The diagnosis of celiac disease is complex and includes symptomatology, serology, small intestinal histology, and genetic status. Serological testing plays a central role within the diagnostic procedure and is based on the measurement of disease-specific antibodies against gluten proteins (antigen) and tissue transglutaminase (autoantigen). Immunofluorescence detection and enzyme-linked immunosorbent assays are currently most often applied for antibody testing. However, these tests are expensive and time-consuming. Therefore, simple and rapid alternative methods have been developed during the last years, and electro-chemical immunosensors seem to be the most promising analytical tools. The architecture of these sensors may comprise the following elements: working and reference electrodes, covalent or noncovalent binding of the antigen to the surface of the working electrode by means of a functional monolayer, and blocking of unreacted binding sites. The analytical procedure is initiated by adding the analyte (serum antibodies) and an analyte-specific second antibody, which is usually labeled with an enzyme. The special reaction of the enzyme with an appropriate substrate results in a product that initiates a current that can be measured by different electrical methods. A number of different electrochemical immunosensors variable in different electrodes, binding systems, secondary antibodies, and current measurements have been developed. Most of them have been tested with real human serum samples of celiac patients and healthy individuals, and some of them reached disease sensitivity and specificity comparable with traditional analytical systems. Thus, electrochemical immunosensors can be promising alternatives to existing diagnostic tests in the future. They are simple, reliable, robust, user-friendly, and cost-effective tools with short operation times.
Localization of Active Caspase-3 and Caspase-8 in Nasal Polyps and Nasal Hyperplasia in Consideration of Mast Cell Function: A Semiquantitatively Analysis  [PDF]
Nadine Franzke, Sibylle Koehler, Peter Middel, Claudia Fuoco, Francesco Cecconi, Fabio Quondamatteo, Rainer Laskawi, Saskia Rohrbach
International Journal of Otolaryngology and Head & Neck Surgery (IJOHNS) , 2012, DOI: 10.4236/ijohns.2012.13014
Abstract: Introduction: The pathogenesis of nasal polyposis and nasal hyperplasia is still unknown. The localization of caspases in nasal polyps and nasal hyperplasia of patients with and without allergic rhinitis was studied. Methods: Sections of human nasal polyps (n = 5) and hyperplastic nasal turbinates (5 with, 5 without allergy) were stained for active caspase-3 and caspase-8. Double immunofluorescence was used to evaluate colocalization of the caspases with Ki-M1P and tryptase. TUNEL was performed. Results: Active caspase-3 and caspase-8 were seen in nearly all nasal polyps and hyperplastic nasal turbinates. Active caspase-3 was predominantly localized in stromal cells, identified as mast cells. Caspase-8 was localized in mast cells with the pattern similar to active caspase-3 and additionally found in epithelial cells at the nasal and polyp surface and in epithelial cells of glands. Conclusion: Our results suggest that mast cell apoptosis may be involved in the pathological mechanisms which characterize and sustain chronic inflammatory disorders of the nasal mucosa with and without allergy.
Reviewing the environmental and human health knowledge base of carbon nanotubes
Helland,Aasgeir; Wick,Peter; Koehler,Andreas; Schmid,Kaspar; Som,Claudia;
Ciência & Saúde Coletiva , 2008, DOI: 10.1590/S1413-81232008000200019
Abstract: carbon nanotubes (cnts) are one of the most promising materials in nanotechnology. the various synthesis, purification and postprocessing methods produce cnts with diverse physical characteristics, appliable in many fields. their extensive projected use makes it important to understand their potential harmful effects. besides showing a notable range of results of some toxicology studies, this review concluded that: a) there are different types of cnts; thus, they cannot be considered a uniform group of substances; and b) in environmental compartments, cnts can be bioavailable to organisms. their properties suggest a possible accumulation along the food chain and high persistence. in organisms, cnt absorption, distribution, metabolism, excretion and toxicity depend on the inherent physical and chemical characteristics (e.g., functionalization, coating, length and agglomeration state), influenced by external environmental conditions during cnt production, use, and disposal. thus, characterized exposure scenarios could be useful in toxicology studies. however, upon reaching the lungs in enough quantity, cnts produce a toxic response (time and dose-dependent). the risks to human health and environment should be identified for a successful introduction of cnts in future applications.
Simple trachelectomy of early invasive cervix carcinoma in the second trimester
Radek Chvatal,Peter Oppelt,Christian Koehler,Alvin Habelsberger
Journal of the Turkish-German Gynecological Association , 2011,
Abstract: Although cervical carcinoma is among the most frequently encountered malignancies during pregnancy only a small number of cases during pregnancy have been reported. Usually, the patients have been treated by radical trachelectomy with or without chemotherapy during the pregnancy.Laparoscopic pelvic lymph node dissection with frozen section, simple trachelectomy and cerclage were performed in the 22nd week of pregnancy. The histologic examination confirmed a squamous cell carcinoma of the cervix of 35mm diameter, lymphangioinvasion (L1), low grade, clear surgical margin, negative pelvic lymph nodes according to stage Figo IB. Adjuvant chemotherapy with three cycles of cisplatin was performed after surgery. Delivery was performed by cesarean section followed by radical hysterectomy in the the 32nd week of pregnancy. Recurrent adjuvant chemotherapy with three cycles of cisplatin and local vaginal iridium radiation were performed after surgery. Patient had no surgery related complications. No relapse of cancer has been diagnosed during the following 16 months.Simple trachelectomy may be alternative treatment option to radical trachelectomy for pregnant women with early stage cervical cancer without lymph node metastasis.
Uv induced ds(ss)-DNA damage: optical and electrical recognition
Veligura Alina,Koehler Michael,Fritzsche Wolfgang,Lytvyn Peter
BMC Plant Biology , 2005, DOI: 10.1186/1471-2229-5-s1-s32
Abstract:
Identification of Intact High Molecular Weight Glutenin Subunits from the Wheat Proteome Using Combined Liquid Chromatography-Electrospray Ionization Mass Spectrometry
Bert Lagrain, Markus Brunnbauer, Ine Rombouts, Peter Koehler
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0058682
Abstract: The present paper describes a method for the identification of intact high molecular weight glutenin subunits (HMW-GS), the quality determining proteins from the wheat storage proteome. The method includes isolation of HMW-GS from wheat flour, further separation of HMW-GS by reversed-phase high-performance liquid chromatography (RP-HPLC), and their subsequent molecular identification with electrospray ionization mass spectrometry using a quadrupole-time-of-flight mass analyzer. For HMW-GS isolation, wheat proteins were reduced and extracted from flour with 50% 1-propanol containing 1% dithiothreitol. HMW-GS were then selectively precipitated from the protein mixture by adjusting the 1-propanol concentration to 60%. The composition of the precipitated proteins was first evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis with Coomassie staining and RP-HPLC with ultraviolet detection. Besides HMW-GS (≥65%), the isolated proteins mainly contained ω5-gliadins. Secondly, the isolated protein fraction was analyzed by liquid chromatography-mass spectrometry. Optimal chromatographic separation of HMW-GS from the other proteins in the isolated fraction was obtained when the mobile phase contained 0.1% trifluoroacetic acid as ion-pairing agent. Individual HMW-GS were then identified by determining their molecular masses from the high-resolution mass spectra and comparing these with theoretical masses calculated from amino acid sequences. Using formic acid instead of trifluoroacetic acid in the mobile phase increased protein peak intensities in the base peak mass chromatogram. This allowed the detection of even traces of other wheat proteins than HMW-GS in the isolated fraction, but the chromatographic separation was inferior with a major overlap between the elution ranges of HMW-GS and ω-gliadins. Overall, the described method allows a rapid assessment of wheat quality through the direct determination of the HMW-GS composition and offers a basis for further top-down proteomics of individual HMW-GS and the entire wheat glutenin fraction.
Structure and Stability of Chemically Modified DNA Bases: Quantum Chemical Calculations on 16 Isomers of Diphosphocytosine
Abdullah G. Al-Sehemi,Tarek M. El-Gogary,Karl Peter Wolschann,Gottfried Koehler
ISRN Physical Chemistry , 2013, DOI: 10.1155/2013/146401
Abstract:
Structure and Stability of Chemically Modified DNA Bases: Quantum Chemical Calculations on 16 Isomers of Diphosphocytosine
Abdullah G. Al-Sehemi,Tarek M. El-Gogary,Karl Peter Wolschann,Gottfried Koehler
ISRN Physical Chemistry , 2013, DOI: 10.1155/2013/146401
Abstract: We studied for the first time 16 tautomers/rotamers of diphosphocytosine by four computational methods. Some of these tautomers/rotamers are isoenergetic although they have different structures. High-level electron correlation MP2 and MP4(SDQ) ab initio methods and density functional methods employing a B3LYP and the new M06-2X functional were used to study the structure and relative stability of 16 tautomers/rotamers of diphosphocytosine. The dienol tautomers of diphosphocytosine are shown to be much more stable than the keto-enol and diketo forms. The tautomers/rotamers stability could be ranked as PC3?=?PC12?<?PC2?=?PC11?<?PC1?<?PC10?<?PC8?<?PC9?<?PC15?<?PC16?<?PC6?~?PC7?<?PC13?<?PC4?~?PC14?<?PC5. This stability order was discussed in the light of stereo and electronic factors. Solvation effect has been modeled in a high dielectric solvent, water using the polarized continuum model (PCM). Consideration of the solvent causes some reordering of the relative stability of diphosphocytosine tautomers: PC3?~?PC12?~?PC2?~?PC11?<?PC1?<?PC10?<?PC8?<?PC9?<?PC15?~?PC16?<?PC13?<?PC6?~?PC7?~?PC14?<?PC4?~?PC5. 1. Introduction DNA is a naturally occurring biological macromolecule, containing thousands of nucleic acid bases, and it is of prime importance in genetic determination [1]. The five nucleic acid bases, cytosine, thymine, uracil, adenine, and guanine, found in DNA and RNA control the replication of DNA, store information required to synthesize proteins, and translate this information to the protein. Tautomerism is a well-known phenomenon occurring in nucleic acid bases [2–16], in which proton transfer from the heterocyclic ring center to an exocyclic oxo- or imino- group leads to the formation of either an –OH or an –NH2 groups. These processes are known as keto-enol or imino-amino tautomerism, respectively. Tautomerism, a sort of isomerism, plays an important role in organic chemistry, medicinal chemistry, pharmacology, and molecular biology. Tautomerism partially explains the structure of nucleic acids and their mutations [17]. In DNA bases, tautomerization results in altered base pairing configurations or mispairing due to changes in hydrogen-bonding capabilities. DNA mutations are likely to be caused by such alterations. Cytosine is one of the building pyrimidine nucleobases of RNA. A large amount of experimental [18–34] and theoretical work [35–58] has been carried out in order to elucidate the structure of cytosine and its tautomers. Chemically modified bases have attracted extensive interest due to their numerous pharmacological, biochemical, and
The van der Waals Potential between Metastable Atoms and Solid Surfaces: Novel Diffraction Experiments versus Theory
Ruediger Bruehl,Peter Fouquet,Robert E. Grisenti,J. Peter Toennies,; Gerhard C. Hegerfeldt,Thorsten Koehler,Martin Stoll,Christian Walter
Physics , 2001, DOI: 10.1209/epl/i2002-00202-4
Abstract: Highly polarizable metastable He* ($\mathrm{2^3S}$) and Ne* ($\mathrm{2^3P}$) atoms have been diffracted from a 100 nm period silicon nitride transmission grating and the van der Waals coefficients $C_3$ for the interaction of the excited atoms with the silicon nitride surface have been determined from the diffraction intensities out to the 10th order. The results agree with calculations based on the non-retarded Lifshitz formula.
Digital libraries and World Wide Web sites and page persistence.
Wallace Koehler
Information Research: an international electronic journal , 1999,
Abstract: Web pages and Web sites, some argue, can either be collected as elements of digital or hybrid libraries, or, as others would have it, the WWW is itself a library. We begin with the assumption that Web pages and Web sites can be collected and categorized. The paper explores the proposition that the WWW constitutes a library. We conclude that the Web is not a digital library. However, its component parts can be aggregated and included as parts of digital library collections. These, in turn, can be incorporated into "hybrid libraries." These are libraries with both traditional and digital collections. Material on the Web can be organized and managed. Native documents can be collected in situ, disseminated, distributed, catalogueed, indexed, controlled, in traditional library fashion. The Web therefore is not a library, but material for library collections is selected from the Web. That said, the Web and its component parts are dynamic. Web documents undergo two kinds of change. The first type, the type addressed in this paper, is "persistence" or the existence or disappearance of Web pages and sites, or in a word the lifecycle of Web documents. "Intermittence" is a variant of persistence, and is defined as the disappearance but reappearance of Web documents. At any given time, about five percent of Web pages are intermittent, which is to say they are gone but will return. Over time a Web collection erodes. Based on a 120-week longitudinal study of a sample of Web documents, it appears that the half-life of a Web page is somewhat less than two years and the half-life of a Web site is somewhat more than two years. That is to say, an unweeded Web document collection created two years ago would contain the same number of URLs, but only half of those URLs point to content. The second type of change Web documents experience is change in Web page or Web site content. Again based on the Web document samples, very nearly all Web pages and sites undergo some form of content within the period of a year. Some change content very rapidly while others do so infrequently (Koehler, 1999a). This paper examines how Web documents can be efficiently and effectively incorporated into library collections. This paper focuses on Web document lifecycles: persistence, attrition, and intermittence. While the frequency of content change has been reported (Koehler, 1999a), the degree to which those changes effect meaning and therefore the integrity of bibliographic representation is yet not fully understood. The dynamics of change sets Web libraries apart from the traditional library
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