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Biomedical subjects

J Rothe

Publications and source records attributed to J Rothe.

At least 19 recordsLinked to original sources
PubMed2002

Low temperature XAFS investigation on the lutetium binding changes during the 2-line ferrihydrite alteration process.

The time dependent changes of Lu speciation (used as Am(III) homologue), initially sorbed onto 2-line ferrihydrite at pH 5.9, during tempering (70 degrees C) to stable crystalline transformation products, goethite and hematite, is studied. Microscopies (AFM, SEM), XRD and FTIR spectroscopy confirm transformation to both goethite and hematite, with a predominance of hematite. XRD investigation of another transformation series at pH 8.0 (75 degrees C, [Lu(III)initial] 7 times higher) shows that the cell volume of hematite increases, suggesting the incorporation of Lu in the crystal structure. Extended X-ray absorption fine structure (EXAFS) (pH 5.9 series, 70 degrees C) reveals a shortening of the Lu-O bond distance and an increase in asymmetry of the first shell with increasing tempering time in the intermediate temper time samples. The intensity of the second peak in the Fourier transform (FT) of the EXAFS increases and splits into two components. The EXAFS data of the end product can be modeled well using a hematite-like cluster, with an isotropic expansion of distances to account for incorporation of Lu into the hematite structure. These results demonstrate that the Lu is incorporated in the crystal lattice of the transformation product, as opposed to being occluded or remaining a sorbed species on the surface.

Absorptiometry, Photon↗
PubMed2002

XAFS investigation of the structure of aqueous thorium(IV) species, colloids, and solid thorium(IV) oxide/hydroxide.

X-ray absorption fine structure (XAFS) spectroscopy at the Th L3 edge is applied for the characterization of crystalline, anhydrous ThO(2)(cr), microcrystalline ThO(2).xH(2)O(s), amorphous ThO(n)(OH)(4-2n).xH(2)O(am), aqueous Th(IV) solutions, and colloidal suspensions up to p(c)H 3.7. The microcrystalline, possibly hydrated thorium dioxide, is formed at p(c)H 1.5-2.5 by precipitation from suspensions of 16-23 nm thorium dioxide colloids. The solubility data determined for this solid is several orders of magnitude lower than the values for amorphous Th(IV) hydroxide or hydrous oxide. The EXAFS spectrum of the isolated microcrystalline particles shows that their structure is different from that of anhydrous crystalline ThO(2)(cr) and amorphous ThO(n)(OH)(4-2n).xH(2)O(am) precipitated at higher pH and dried at room temperature. The solubility measured for the amorphous Th(IV) precipitate is comparable to that previously reported for a solid prepared in a similar manner. In other solubility studies with amorphous Th(IV) hydroxide or hydrous oxide, considerably higher thorium concentrations are measured at p(c)H 3.5-5. The aqueous speciation is made by EXAFS for solutions prepared by careful coulometric titration under comparable conditions (p(c)H and thorium concentration). The spectra of these solutions demonstrate the presence of a large amount of Th(IV) polynuclear species or colloids of small size, having a highly asymmetric Th-O coordination. The EXAFS spectrum of these colloids is similar to that of the amorphous solid.

Journal Article↗
PubMed2000

Soft X-Ray Spectromicroscopy Investigation of the Interaction of Aquatic Humic Acid and Clay Colloids.

Soft X-ray spectromicroscopy investigations of the interaction of aquatic humic acid (HA) and montmorillonite colloids have been performed in situ at the NSLS X1-A STXM endstation. Images have been recorded of montmorillonite particles, HA aggregates, and mixed suspensions of both montmorillonite + HA and montmorillonite + carboxyl polystyrene microspheres, as reference organic colloids. Special emphasis has been placed on the sample preparation technique in order to keep the colloid particles hydrated during all measurements. C 1s near edge absorption fine structure extracted from STXM image stacks reveals electronic transitions corresponding to functional -COOH and -C(6)H(5) groups present in HA and polystyrene. XANES peak intensities reflect the relative amounts of these two carbon functional groups in the organic particles. For example, the greater amount of carboxyl groups in HA compared to the latex reference particles affects a larger 1s-->pi* transition intensity. A specific form of montmorillonite-HA particle agglomeration at near-neutral pH has been observed. Under these conditions, we found no separate clustering of HA. Instead, STXM images show the HA to coat the clay mineral surface, leading to nearly a fractal manner of aggregation. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Do stable isotopes reflect the food web development in regenerating ecosystems?

We evaluated the use of delta15N- and delta13C-values to monitor the development of food web complexity and biodiversity in a regenerating ecosystem. Therefore a model food chain was established feeding cultivated woodlice (Porcellio dilatatus) on a cellulolytic fungus (Chaetomium globosum) grown on cellulose paper. Two diets of different quality (C:N ratios of 54 vs. 200) with different delta15N- (1.3% vs. 3.1%) but identical delta13C-values caused low and high dietary stress in animals of treatment A and B, respectively. After an incubation time of 7 weeks amount, elemental and isotopic composition of collected faeces and exuviae as well as woodlice and remaining food were determined. The increase of delta15N-values of woodlice relative to the diet was 5.7% and 2.5% in treatments A and B, respectively, whereas delta13C-shifts were 1.0% and 1.6%, showing a reverse relationship. Modelling of elemental and isotopic mass balances indicated that faeces recycling explains the unexpected high 15N-enrichments. Moreover, 13C-enrichments were positively correlated to the degree of starvation. Considering the effects of starvation and recycling of faeces, stable isotopes represent a useful tool to elucidate trophic interactions in regenerating food webs.

Animals↗
PubMed1996

X-ray absorption and X-ray photoelectron spectroscopy of a rhodium colloid.

Transition metal colloids are potential precursors of heterogeneous catalysts with application to selective chemical reactions. Sample preparation techniques are described. Experimental details are given of the characterization of these often air-sensitive particles by X-ray photoelectron and X-ray absorption spectroscopy. First results obtained with both techniques for a Rh-colloid show that the metal is mainly present in the zerovalent chemical state. But the spectra indicate further chemical states of Rh which can be assigned to the outermost metal atoms of the colloid interacting with organic ligands or to the educt Rh-halides.

Journal Article↗
PubMed1995

Early interleukin 12 production by macrophages in response to mycobacterial infection depends on interferon gamma and tumor necrosis factor alpha.

Interleukin 12 (IL-12) produced by macrophages immediately after infection is considered essential for activation of a protective immune response against intracellular pathogens. In the murine Mycobacterium bovis Bacillus Calmette-Guérin (BCG) model we assessed whether early IL-12 production by macrophages depends on other cytokines. In vitro, murine bone marrow-derived macrophages produced IL-12 after infection with viable M. bovis BCG or stimulation with LPS, however, priming with recombinant interferon gamma (rIFN-gamma) was necessary. In addition, IL-12 production by these macrophages was blocked by specific anti-tumor necrosis factor alpha (TNF-alpha) antiserum. Macrophages from gene deletion mutant mice lacking either the IFN-gamma receptor or the TNF receptor 1 (p55) failed to produce IL-12 in vitro after stimulation with rIFN-gamma and mycobacterial infection. In vivo, IL-12 production was induced in spleens of immunocompetent mice early during M. bovis BCG infection but not in those of mutant mice lacking the receptors for IFN-gamma or TNF. Our results show that IL-12 production by macrophages in response to mycobacterial infection depends on IFN-gamma and TNF. Hence, IL-12 is not the first cytokine produced in mycobacterial infections.

Animals↗
PubMed1994

Differential responses of fibroblasts from wild-type and TNF-R55-deficient mice to mouse and human TNF-alpha activation.

The role of the two TNF receptor types, TNF-R55 and TNF-R75, was studied on mouse fibroblasts, taking advantage of TNF-R55-deficient mice generated by gene targeting (Tnfr1 degree-mice), and selectivity of human TNF-alpha for mouse TNF-R55. Radioligand binding assays showed that both TNF receptors were expressed on wild-type mouse fibroblasts, whereas normal levels of TNF-R75 were expressed on mouse fibroblasts isolated from Tnfr1 degree-mice. It was found that TNF-R55 controlled four major TNF-induced fibroblast functions: (1) adhesion to leukocyte cell lines as well as ICAM-1, VCAM-1, CD44, and MHC class I up-regulation; (2) secretion of other cytokines as demonstrated by stimulated IL-6 and granulocyte-macrophage-CSF releases; (3) cell proliferation; and (4) NF-kappa B activation. Stimulation through TNF-R75, in TNF-R55-deficient fibroblasts, did not have any effect in these functions. In general, mouse TNF-alpha (recognizing both mouse TNF receptors) had a higher sp. act. than human TNF-alpha (recognizing only mouse TNF-R55) in wild-type fibroblasts, whereas both mouse and human TNF-alpha had similar cytotoxic activities in WEHI 164 cells.

Animals↗
PubMed1994

Establishment of the role of IL-6 and TNF receptor 1 using gene knockout mice.

Cytokines are known to be key players in host response to infection, immunological disorders, and tissue injury in the attempt of an organism to overcome the insult and restore homeostasis. Another important aspect of cytokines, however, is their normal physiological role during development in the unchallenged organism. The most elegant way to analyze both of these functions is to introduce targeted mutations in embryonic stem cells in order to create new mouse strains deficient for a given cytokine and identify the functions that are consequently impaired or lost. This review summarizes the mutant phenotypes of mice carrying a null mutation in the cytokine IL-6 gene or the tumor necrosis factor receptor 1 (Tnfr1) gene. Results for interferon-- and interferon-gamma receptor-deficient mice are included for comparison.

Acute-Phase Reaction↗
PubMed1994

Phenotypic analysis of TNFR1-deficient mice and characterization of TNFR1-deficient fibroblasts in vitro.

In order to analyse the physiological relevance of the 55 kDa tumor necrosis factor receptor 1 (TNFR1) and its role in various TNF related pathological conditions, such as septic shock, we have generated mice by gene targeting deficient for TNFR1 expression. The TNFR1-deficient mice are unable to cope with Listeria monocytogenes infections but mount an apparently normal immune response when challenged with Vaccinia or LCMV viruses. They are resistant to the lethal effects of lipopolysaccharide (LPS) after sensitization with D-galactosamine (D-GalN) but remain sensitive to very high doses of LPS given alone. We have analyzed functions relevant to inflammatory processes, such as adhesion, secondary factor release, and proliferation in fibroblasts derived from these mice. We show that the TNFR1 virtually monopolises TNF-mediated signaling in all these situations and that the 75 kDa TNFR2 seems to be largely restricted to an accessory role, which is compatible with the previously established "ligand passing" hypothesis.

Alleles↗
PubMed1993

Mice lacking the tumour necrosis factor receptor 1 are resistant to TNF-mediated toxicity but highly susceptible to infection by Listeria monocytogenes.

Tumour necrosis factor (TNF), jointly referring to TNF alpha and TNF beta, is a central mediator of immune and inflammatory responses; its activities are mediated by two distinct receptors, TNFR1 (p55) and TNFR2 (p75) (reviewed in refs 1-3). The cytoplasmic domains of the TNFRs are unrelated, suggesting that they link to different intracellular signalling pathways. Although most TNF responses have been assigned to one or the other of the TNF receptors (mostly TNFR1), there is no generally accepted model for the physiological role of the two receptor types. To investigate the role of TNFR1 in beneficial and detrimental activities of TNF, we generated TNFR1-deficient mice by gene targeting. We report here that mice homozygous for a disrupted Tnfr1 allele (Tnfr1(0)) are resistant to the lethal effect of low doses of lipopolysaccharide after sensitization with D-galactosamine, but remain sensitive to high doses of lipopolysaccharide. The increased susceptibility of Tnfr1(0)/Tnfr1(0) mutant mice to infection with the facultative intracellular bacterium Listeria monocytogenes indicates an essential role of TNF in nonspecific immunity.

Animals↗
PubMed1993

Genomic organization and promoter function of the murine tumor necrosis factor receptor beta gene.

Using the tumor necrosis factor receptor beta (TNFR beta) cDNA as a probe, overlapping clones from a genomic phage library were isolated which encompass the murine TNF receptor beta gene. Analysis of the gene led to the identification of 10 exons, most of which were concentrated in two clusters. The boundaries of the exons do not match protein domains or characteristic motifs of the extracellular region of the TNFR beta. The 5'-flanking region of the gene shows a high density of G and C nucleotides with a strong overrepresentation of CpG dinucleotides. Most of the analyzed CpG were found to be nonmethylated, suggesting that this region is an HTF island. We revealed at least three transcriptional start sites which is likely due to the absence of classical TATA and CAAT sequences from the putative promoter region. CAT assays confirmed promoter activity of the 5'-flanking sequences. Surprisingly, some successively shortened promoter constructs displayed higher relative promoter activity than a full length clone. Preliminary experiments indicate that the promoter region of the TNFR beta gene does not respond to a variety of cytokines. In summary, the structural and functional analysis suggest that the TNFR beta expression is directed by a non-inducible housekeeping-type promoter.

Animals↗
PubMed1993

Functional expression of a human TCR beta gene in transgenic mice.

A functionally rearranged TCR beta (Tcrb) gene was isolated from a cloned human T helper cell recognizing the CS.T3 epitope of Plasmodium falciparum with HLA-DR2. Transgenic mice were generated by co-injection of the human gene together with the mouse Tcrb enhancer. Analysis of transgenic mice shows that the functional Tcrb gene of xenogenic, i.e. human, origin exerts allelic exclusion of endogenous Tcrb genes. Cytofluorometric analysis revealed expression of the human TCR beta chain on virtually all thymocytes and peripheral T cells together with endogenous TCR beta chains and CD3 components. No surface expression of mouse TCR beta chain or rearrangement of endogenous Tcr genes was detectable. Expression of the hybrid receptor causes a reduction in the number of thymocytes and a bias for CD4+CD8- T cells in the thymus as compared with non-transgenic littermates. Peripheral transgenic T cells mount a normal proliferative response against allogeneic targets in mixed lymphocyte reactions. These results show that a hybrid mouse/human TCR is able to pass positive and negative selection in the thymus, and is functional in transgenic mice.

Animals↗
PubMed1992

Tumor necrosis factor receptors--structure and function.

Tumor necrosis factors (TNFs) have been a focus of research for well over a decade now. The identification and recent molecular cloning of two different types of cell-surface TNF receptors will shed further light on the mode of action of these pleiotropic cytokines. In the present article, we summarize the data on the biochemistry and structure of the receptors and focus on the molecular cloning of the respective cDNAs. The nucleotide sequences of the receptor genes revealed that both TNF receptors belong to the still growing nerve growth factor receptor gene family. The function and origin of TNF inhibitory proteins as well as receptor-mediated signal transduction are discussed.

Animals↗
PubMed1990

A molecular and structural analysis of the VH and VK regions of monoclonal antibodies bearing the A48 regulatory idiotype.

The results presented in this paper explore the molecular basis for expression of the A48 regulatory Id (RI). A48 RI+ mAb derived from idiotypically manipulated mice molecularly resembled the A48 and UPC 10 prototypes of this system by utilizing a VHX24-Vk10 combination. Id expression by these antibodies was not restricted by a particular D region sequence, JH, or JK segment, but quantitative differences in Id expression were associated with utilization of different members of the VK10 germ-line gene families. The VL sequences of these A48 RI+ mAb has identified amino acid residues lying in four different idiotope-determining regions which may contribute to the structural correlate of this Id. A comparative sequence analysis of the VH regions of these VHX24 utilizing A48 RI+ mAb with several A48 RI+ mAb utilizing VHJ558 or VH7183 VH genes as well as a hybrid transfectoma antibody derived from two A48 RI-, VHJ558 utilizing hybridomas, all suggested that four nonconsecutive positions which lie outside the idiotope-determining regions may contribute structural elements toward expression of this Id. The VH and VL regions of the A48RI+, VHX24-Vk 10+ mAb showed low to moderate levels of somatic mutation which showed different patterns of distribution between the complementary determining region (CDR) and framework regions in the H and L chains. Although the VK sequences contained 50% of the replacement mutations in the CDR, with a replacement/silent mutation ratio of 10, the CDR of the VH sequences contained only 31% of the replacement mutations with a replacement/silent mutation ratio of 0.69.

Amino Acid Sequence↗