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Competition Tests (competition + test)

Distribution by Scientific Domains

Medical Sciences	60%

Selected Abstracts

Competition Tests with a Non-Structural Model: the Panzar,Rosse Method Applied to Germany's Savings Banks

GERMAN ECONOMIC REVIEW, Issue 1 2009
Horst Gischer
Banking; competition; market behaviour Abstract. In this paper we adopt the Panzar,Rosse approach to assess the competitive conditions in the German banking market for the period from 1993 to 2002. We suggest several improvements to the empirical application of the approach and show that frequently used empirical models that apply price rather than revenue functions lead to biased results. Using disaggregated annual data from more than 400 savings banks (Sparkassen) the empirical findings indicate monopolistic competition, the cases of monopoly and perfect competition are strongly rejected. Furthermore, small banks seem to enjoy even more market power than larger institutions. [source]

Assessment of CD8 involvement in T,cell clone avidity by direct measurement of HLA-A2/Mage3 complex density using a high-affinity TCR like monoclonal antibody

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 10 2005
Karine Bernardeau
Abstract Peptide affinity for MHC molecules determines the number of MHC/peptide complexes stabilized at the cell surface in in vitro tests or in vaccination protocols. We isolated a high affinity monoclonal antibody specific for the HLA-A2/Mage3 complex that enables an equilibrium binding assay to be performed on T2 cell line loaded with a range of Mage3 peptides. Binding of Mage3 to the HLA-A2 molecule can be modeled by a standard receptor-ligand interaction characterized by an affinity constant. This model enables the measurement of the affinity of other immunogenic peptides for HLA-A2 by a competition test and the calculation of the density of complexes stabilized at the T2 cell surface for all peptide concentrations. Quantification of the HLA-A2/Mage3 complexes at target cell surfaces was used to estimate the number of complexes required to reach cytotoxicity ED50 of human T,cell clones sorted from an unprimed repertoire. We confirm with this antibody the direct relationship between clone avidity and TCR affinity, and the moderate contribution of the CD8 co-receptor in the reinforcement of TCR-MHC/peptide contact. Nevertheless, CD8 plays a critical role in the amplification of the specific signal to establish an efficient T,cell response at low specific complex densities found in physiological situations. [source]

Novel estrogen receptor ligands and their structure,activity relationship evaluated by scintillation proximity assay for high-throughput screening

DRUG DEVELOPMENT RESEARCH, Issue 4 2005
Ling He
Abstract The estrogen receptor (ER) is an important drug target with allosteric characteristics that binds orthotopic hormones and other ligands. A recently developed scintillation proximity (SPA)-based assay for high-throughput screening (HTS) of compound libraries was used to identify novel estrogen receptor ligands that might have ER subtype selective binding activity. Radioligand binding was determined in a multi-detector scintillation counter designed for microtitration plates. Equilibrium binding experiments and kinetic competition tests were performed with [3H]-estradiol and human ER, and ER, receptors. A library of 6,000 structurally diverse compounds was screened. From this, several novel ligands were identified that showed pronounced subtype-selective differences in ligand binding for ER, and ER,. The observed equilibrium dissociation constant (Kd) for the binding of [3H]estradiol to ER, and ER, receptors were approximately 0.25 and 0.64 nM, respectively. When 17,-estradiol, raloxifene and daidzein were tested for binding affinity to ER, in a competition assay, the IC50 values were 0.34, 1.31, and 75.6 nM, respectively. When tested for binding affinity to ER,, the IC50 values were 1.05, 11.4, and 10.6 nM, respectively. The results obtained show that the methodology is valid in comparison to previously published data regarding estradiol and other standard compounds (raloxifene and daidzein) binding characteristics of estrogen receptors. The assay is also well suited to applied research as a tool in HTS of compound libraries in the search of ER ligands. Several novel active compounds were identified and selected as potent ER subtype ligands. Drug Dev Res 64:203,212, 2005. © 2005 Wiley-Liss, Inc. [source]

Urea Sensitization Caused by Separation of Helicobacter pylori RNA Polymerase , and ,, Subunits

HELICOBACTER, Issue 2 2007
Daiva Dailidiene
Abstract Background:, The , and ,, subunits of RNA polymerase are fused in all Helicobacters, but separate in most other taxa. Prior studies had shown that this fusion is not essential for viability in culture or in vivo, but had not tested it for potentially important quantitative effects on phenotype. Methods:, The effect of separating rpoB and rpoC sequences on Helicobacter pylori growth was tested in culture and during mouse infection. Results:, Derivatives of strains X47 and SS1 carrying this "rpoBCsplit" allele colonized mice less vigorously than their wild-type parents in competition tests. With X47 rpoBCsplit, this reduced vigor was evident in wild-type mice, whereas with SS1 rpoBCsplit it was seen only in cytokine IL-10- and IL-12,-deficient mice. In culture, the rpoBCsplit allele sensitized each of four strains tested (X47, SS1, 88-3887, and AM1) to urea, a metabolite that is secreted into the gastric mucosa; urea sensitization was more severe in X47 than in SS1 genetic backgrounds. The rpoBCsplit allele also caused poorer growth on Ham's F12 agar, a nutritionally limiting medium, but had little effect on sensitivity to mild acidity. Conclusions:,H. pylori's normal RNA polymerase ,-,, subunit fusion contributes quantitatively to fitness. We propose that urea, although important to H. pylori in vivo, also be considered inhibitory; and that H. pylori's natural ,-,, subunit fusion helps it cope with urea exposure. [source]

Effects of hippocampal cholinergic deafferentation on learning strategy selection in a visible platform version of the water maze

HIPPOCAMPUS, Issue 6 2003
J.L. Bizon
Abstract Recent evidence has suggested that the relative levels of acetylcholine (ACh) between brain structures may be an important factor in the choice of behavioral strategy in settings in which either hippocampal or dorsal striatal brain systems can be employed both effectively and independently (McIntyre and Gold. 1999. Soc Neurosci Abs 25:1388). The current investigation used the neurotoxin 192 IgG-saporin to deplete the hippocampus of ACh selectively, while leaving ACh in other brain regions, including dorsal striatum, intact. Rats were then trained on a version of the Morris water maze, in which behavioral strategies attributed to the hippocampus and dorsal striatum are placed in direct competition. It was predicted that rats with hippocampal ACh depletion would display a cue bias. Contrary to this prediction, depleting hippocampal ACh did not bias against and, in fact, promoted use of a hippocampal place strategy in this task, as indicated by choice in competition tests and performance on hidden platform training trials. These data add to a growing literature demonstrating that the septohippocampal cholinergic system is not required for accurate spatial learning and suggest a complex role for basal forebrain projections in processing information about the spatial environment. © 2003 Wiley-Liss, Inc. [source]