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B Denecke

Publications and source records attributed to B Denecke.

10 recordsLinked to original sources
PubMed2000

Improvements in quantitative source preparation

Quantitative source preparation is indispensable for radionuclide standardisation. To improve the source quality, a device has been developed to accelerate the evaporation of solvents from a drop deposited on a substrate. Short drying times were reached by stirring the rotating drop with multiple jets of dry nitrogen at elevated temperature. Uniform deposits with a large number of small crystals were obtained. The source-quality was checked by micrographs and scans of autoradiographs and by the shape parameters of alpha-particle spectra.

Journal Article↗
PubMed2000

Determination of the absolute alpha-particle emission probabilities of 237Np

In the framework of the EUROMET project No. 416, decay scheme data of 237Np were measured by alpha-particle spectrometry. Emission probabilities of alpha-particles and gamma-rays were determined in the past at IRMM. After improvements of the detector system and the electron bending magnet the alpha-particle measurements have been repeated. As a result, the absolute emission probabilities of 20 alpha-particle transitions were obtained with a significant lower uncertainty. Among those transitions already known, five new were found.

Journal Article↗
PubMed2000

Standardisation of 204Tl at IRMM

IRMM participated in a recent international comparison for the standardisation of a 204Tl solution organised by BIPM. The activity concentration of the 204Tl solution was measured at IRMM using 3 independent methods; Liquid Scintillation Counting using the CIEMAT/NIST method, 4pi-CsI counting and 4pibeta counting using a large pressurised proportional counter. This article describes the measurements in detail and discusses potential problems in the standardisation of 204Tl.

Journal Article↗
PubMed1999

RGS1 is expressed in monocytes and acts as a GTPase-activating protein for G-protein-coupled chemoattractant receptors.

The leukocyte response to chemoattractants is transduced by the interaction of transmembrane receptors with GTP-binding regulatory proteins (G-proteins). RGS1 is a member of a protein family constituting a newly appreciated and large group of proteins that act as deactivators of G-protein signaling pathways by accelerating the GTPase activity of G-protein alpha subunits. We demonstrate here that RGS1 is expressed in human monocytes; by immunofluorescence and subcellular fractionation RGS1 was localized to the plasma membrane. By using a mixture of RGS1 and plasma membranes, we were able to demonstrate GAP activity of RGS1 on receptor-activated G-proteins; RGS1 did not affect ligand-stimulated GDP-GTP exchange. We found that RGS1 desensitizes a variety of chemotactic receptors including receptors for N-formyl-methionyl-leucyl-phenylalanine, leukotriene B4, and C5a. Interaction of RGS proteins and ligand-induced G-protein signaling can be demonstrated by determining GTPase activity using purified RGS proteins and plasma membranes.

Animals↗
PubMed1999

A cytoplasmic structure resembling large protein aggregates induced by interferons.

IFP 35 is an interferon (IFN)-regulated leucine zipper protein, expression of which is observed in a variety of cell types including monocytes/macrophages, epithelial cells and fibroblasts. Using immunofluorescence studies, we demonstrate that IFP 35 is found in characteristic punctate cytoplasmic structures after IFN treatment. Co-localization experiments using double immunofluorescence and confocal laser scanning microscopy failed to show association of IFP 35 with known organelles (mitochondria, peroxisomes, endoplasmic reticulum, lysosomes, endosomes, Golgi complex), ribosomes, or actin filaments. Subcellular fractionation to separate membrane-associated from cytoplasmic proteins demonstrated that IFP 35 localizes to the cytoplasm. Separation of postnuclear supernatant from HeLa cells by gel filtration revealed that IFP 35 eluted at a molecular mass of 200-440 kD, suggesting that IFP 35 is part of protein complexes. Electron microscopic studies showed cytoplasmic clusters of a few aggregates of IFP 35 in IFN-treated cells which were neither associated with nor surrounded by a membrane. A combination of immunoprecipitation and immunofluorescence studies of cells transfected with a hemagglutinin epitope-tagged IFP 35 expression construct demonstrated complex formation and co-localization of endogenous and transfected IFP 35. Taken together, our studies demonstrate that IFP 35 associates with unique cytoplasmic structures that are distinct from known organelles and resemble large protein aggregates.

Blotting, Western↗
PubMed1995

Transcriptional activation of psoriasis-associated cytokeratin K17 by interferon-gamma. Analysis of gamma-interferon activation sites.

The acid cytokeratin K17 is inducible by interferon-gamma (IFN-gamma), a characteristic unique for cytokeratins analysed so far. In this report, we analysed the molecular basis of K17 expression by IFN-gamma in epithelial cells. The 5'-flanking region of the K17 gene (positions -1762 to -13), cloned in front of a chloramphenicol acetyl transferase (CAT) reporter gene construct, conferred responsiveness to IFN-gamma but not IFN-alpha in transient transfection assays. Sequence analysis revealed three putative gamma-interferon activation sites (GAS). Band-shift assays and transient transfections with CAT reporter gene constructs were used to characterize and to dissect the functional importance of each of the putative GAS elements. In the band shift assay, GAS3 (positions -1528 to -1515) was found to bind GAF/STAT91 and to compete with tryptophanyl-tRNA synthetase (IFP53/WRS)-GAS for binding to GAF; in contrast, GAS1 (positions -183 to -171) and GAS2 (positions -290 to -277) were neither able to bind to nor to compete for GAF/STAT91. However, deletion constructs and mutational analysis of CAT reporter gene constructs harbouring the 5'-flanking region (positions -1762 to -111) in front of the heterologous promoter revealed that the distal GAS3 site was dispensible, but that alteration of the GAS1 element rendered the promoter uninducible by IFN-gamma. Surprisingly, transfection of a CAT-reporter gene construct harbouring a promoter segment (positions -111 to +13) devoid of the GAS elements revealed enhanced CAT-gene expression upon IFN-gamma treatment. The interaction of GAS1 with the interferon-responsive promoter region in the physiological context remains to be clarified.

Base Sequence↗
PubMed1994

IFP 35 is an interferon-induced leucine zipper protein that undergoes interferon-regulated cellular redistribution.

We have isolated a new human cDNA, named IFP 35, whose expression is regulated by interferons (IFN). Induction of IFP 35 mRNA in HeLa cells by IFN is due, at least in part, to increased transcription. In response to IFN treatment, the expression of IFP 35 mRNA is seen in a wide range of different cell types, including fibroblasts, macrophages, and epithelial cells. The cDNA sequence encodes a 282-amino acid protein with a deduced molecular mass of 31,130 Da. In vitro translation of mRNA obtained by both in vitro transcription and hybrid selection resulted in the synthesis of a 35-kDa protein. Antisera raised against IFP 35 recognized a protein with an apparent molecular mass of 35 kDa in HeLa cells. Amino acid sequence analysis revealed a leucine zipper motif in an alpha-helical configuration at the extreme amino terminus of IFP 35. Notable IFP 35 is a unique novel leucine zipper protein in that it lacks a basic domain critical for DNA binding. IFP 35 can specifically form homodimers in vitro. Western blot analysis of fractionated cell extracts indicates increased nuclear localization following IFN treatment.

Amino Acid Sequence↗
PubMed1993

Chimeric liver transcription factors LFB1 (HNF1) containing the acidic activation domain of VP16 act as positive dominant interfering mutants.

The transcription factor LFB1 (HNF1) involved in the expression of liver-specific genes is characterized by a serine/threonine-rich activation domain whose transactivation potential differs between mammals and Xenopus. Exchanging the activation domain between the Xenopus and rat LFB1, we produced chimeric transactivators whose activities are primarily determined by the origin of the activation domain. By replacing the serine/threonine-rich activation domain of LFB1 with the acidic activation domain of VP16, we generated transcription factors that act as dominant positive interfering mutants on endogenous LFB1 in differentiated hepatoma cells. As these LFB1/VP16 chimeras show no self-squelching as observed with wild-type LFB1 and increase the activity of saturating LFB1, we postulate that acidic and serine/threonine-rich activation domains use different targets of the basal transcription machinery. Stable transfection of various LFB1 derivatives, including those containing the VP16 transactivation domain, into the dedifferentiated C2 hepatoma cell resulted in cell clones stably expressing LFB1 function. However, as in none of these clones the chromosomal albumin genes are activated, we conclude that the presence of functional LFB1 may not be sufficient to reactivate liver-specific functions lost in dedifferentiated hepatoma cells.

Amino Acid Sequence↗
PubMed1992

Naphthalene degradation via salicylate and gentisate by Rhodococcus sp. strain B4.

Rhodococcus sp. strain B4, isolated from a soil sample contaminated with polycyclic aromatic hydrocarbons, grows with naphthalene as the sole source of carbon and energy. Salicylate and gentisate were identified as intermediates in the catabolism of naphthalene. In contrast to the well-studied catabolic pathway encoded by the NAH7 plasmid of Pseudomonas putida, salicylate does not induce the genes of the naphthalene-degradative pathway in Rhodococcus sp. strain B4. The key enzymes of naphthalene degradation in Rhodococcus sp. strain B4 have unusual cofactor requirements. The 1,2-dihydroxynaphthalene oxygenase activity depends on NADH and the salicylate 5-hydroxylase requires NADPH, ATP, and coenzyme A.

Biodegradation, Environmental↗