Showing papers by "Martin Luther University of Halle-Wittenberg published in 2003"

Efflux‐mediated heavy metal resistance in prokaryotes

Abstract: What makes a heavy metal resistant bacterium heavy metal resistant? The mechanisms of action, physiological functions, and distribution of metal-exporting proteins are outlined, namely: CBA efflux pumps driven by proteins of the resistance–nodulation–cell division superfamily, P-type ATPases, cation diffusion facilitator and chromate proteins, NreB- and CnrT-like resistance factors. The complement of efflux systems of 63 sequenced prokaryotes was compared with that of the heavy metal resistant bacterium Ralstonia metallidurans. This comparison shows that heavy metal resistance is the result of multiple layers of resistance systems with overlapping substrate specificities, but unique functions. Some of these systems are widespread and serve in the basic defense of the cell against superfluous heavy metals, but some are highly specialized and occur only in a few bacteria. Possession of the latter systems makes a bacterium heavy metal resistant.

R-Boundedness, Fourier Multipliers, and Problems of Elliptic and Parabolic Type

Abstract: Introduction Notations and conventions $\mathcal R$-Boundedness and Sectorial Operators: Sectorial operators The classes ${\mathcal{BIP}}(X)$ and $\mathcal H^\infty(X)$ $\mathcal R$-bounded families of operators $\mathcal R$-sectorial operators and maximal $L_p$-regularity Elliptic and Parabolic Boundary Value Problems: Elliptic differential operators in $L_p(\mathbb{R}^n E)$ Elliptic problems in a half space: General Banach spaces Elliptic problems in a half space: Banach spaces of class $\mathcal{HT}$ Elliptic and parabolic problems in domains Notes References.

Mineral surfaces and soil organic matter

Abstract: Summary The organic carbon content of soil is positively related to the specific surface area (SSA), but large amounts of organic matter in soil result in reduced SSA as determined by applying the Brunauer–Emmett–Teller (BET) equation to the adsorption of N2. To elucidate some of the controlling mechanisms of this relation, we determined the SSA and the enthalpy of N2 adsorption of separates with a density > 1.6 g cm−3 from 196 mineral horizons of forest soils before and after removal of organic matter with NaOCl. Likewise, we investigated these characteristics before and after sorption of increasing amounts of organic matter to four mineral soil samples, oxides (amorphous Al(OH)3, gibbsite, ferrihydrite, goethite, haematite), and phyllosilicates (kaolinite, illite). Sorption of organic matter reduced the SSA, depending on the amount sorbed and the type of mineral. The reduction in SSA decreased at larger organic matter loadings. The SSA of the mineral soils was positively related to the content of Fe oxyhydroxides and negatively related to the content of organic C. The strong reduction in SSA at small loadings was due primarily to the decrease in the micropores to which N2 was accessible. This suggests preferential sorption of organic matter at reactive sites in or at the mouths of micropores during the initial sorption and attachment to less reactive sites at increasing loadings. The exponential decrease of the heat of gas adsorption with the surface loading points also to a filling or clogging of micropores at early stages of organic matter accumulation. Desorption induced a small recovery of the total SSA but not of the micropore surface area. Destruction of organic matter increased the SSA of all soil samples. The SSA of the uncovered mineral matrix related strongly to the amounts of Fe oxyhydroxides and the clay. Normalized to C removed, the increase in SSA was small in topsoils and illuvial horizons of Podzols rich in C and large for the subsoils containing little C. This suggests that micropores preferentially associate with organic matter, especially at small loadings. The coverage of the surface of the soil mineral matrix as calculated from the SSA before and after destruction of organic matter was correlated only with depth, and the relation appeared to be linear. We conclude that mineralogy is the primary control of the relation between surface area and sorption of organic matter within same soil compartments (i.e. horizons). But at the scale of complete profiles, the surface accumulation and stabilization of organic matter is additionally determined by its input.

The Biology of the Ets1 Proto-Oncogene

Abstract: The Ets1 proto-oncoprotein is a member of the Ets family of transcription factors that share a unique DNA binding domain, the Ets domain. The DNA binding activity of Ets1 is controlled by kinases and transcription factors. Some transcription factors, such as AML-1, regulate Ets1 by targeting its autoinhibitory module. Others, such as Pax-5, alter Ets1 DNA binding properties. Ets1 harbors two phosphorylation sites, threonine-38 and an array of serines within the exon VII domain. Phosphorylation of threonine-38 by ERK1/2 activates Ets1, whereas phosphorylation of the exon VII domain by CaMKII or MLCK inhibits Ets1 DNA binding activity. Ets1 is expressed by numerous cell types. In haemotopoietic cells, it contributes to the regulation of cellular differentiation. In a variety of other cells, including endothelial cells, vascular smooth muscle cells and epithelial cancer cells, Ets1 promotes invasive behavior. Regulation of MMP1, MMP3, MMP9 and uPA as well as of VEGF and VEGF receptor gene expression has been ascribed to Ets1. In tumors, Ets1 expression is indicative of poorer prognosis.

Molecular Analysis of the Copper-Transporting Efflux System CusCFBA of Escherichia coli

Abstract: The cus determinant of Escherichia coli encodes the CusCFBA proteins that mediate resistance to copper and silver by cation efflux. CusA and CusB were essential for copper resistance, and CusC and CusF were required for full resistance. Replacements of methionine residues 573, 623, and 672 with isoleucine in CusA resulted in loss of copper resistance, demonstrating their functional importance. Substitutions for several other methionine residues of this protein did not have any effect. The small 10-kDa protein CusF (previously YlcC) was shown to be a periplasmic protein. CusF bound one copper per polypeptide. The pink CusF copper protein complex exhibited an absorption maximum at around 510 nm. Methionine residues of CusF were involved in copper binding as shown by site-directed mutagenesis. CusF interacted with CusB and CusC polypeptides in a yeast two-hybrid assay. In contrast to other well-studied CBA-type heavy metal efflux systems, Cus was shown to be a tetrapartite resistance system that involves the novel periplasmic copper-binding protein CusF. These data provide additional evidence for the hypothesis that Cu(I) is directly transported from the periplasm across the outer membrane by the Cus complex.

Early malignant progression of hereditary medullary thyroid cancer.

Abstract: Background An age-related progression from C-cell hyperplasia to medullary thyroid carcinoma is associated with various germ-line mutations in the rearranged during transfection (RET) proto-oncogene that could be used to identify the optimal time for prophylactic surgery. Methods In this European multicenter study conducted from July 1993 to February 2001, we enrolled patients who had a RET point mutation in the germ line, were 20 years of age or younger, were asymptomatic, and had undergone total thyroidectomy after confirmation of the RET mutation. Exclusion criteria were medullary thyroid carcinomas of more than 10 mm in greatest dimension and distant metastasis. Results Altogether, 207 patients from 145 families were identified. There was a significant age-related progression from C-cell hyperplasia to medullary thyroid carcinoma and, ultimately, nodal metastasis in patients whose RET mutations were grouped according to the extracellular- and intracellular-domain codons affected and in those with the ...

Changes in properties of soil-derived dissolved organic matter induced by biodegradation

Abstract: Properties of dissolved organic matter (DOM) determine its biodegradation. In turn, biodegradation changes the properties of the remaining DOM, which may be decisive for the formation of stable organic carbon in soil. To gain information on both mechanisms and controlling factors of DOM biodegradation and the properties of biodegraded DOM, we investigated changes in the composition of 13 different DOM samples extracted from maize straw, forest floors, peats, and agricultural soils during a 90-day incubation using UV absorbance, fluorescence emission spectroscopy, FTIR-spectroscopy, 1 H-NMR spectroscopy, pyrolysis-field ionization mass spectroscopy (Py-FIMS), and 13 C natural abundance before and after incubation. Changes in the DOM properties were related to the extent of biodegradation determined by the release of CO2. Increasing UV absorption and humification indices deduced from fluorescence emission spectra, and increasing portions of aromatic H indicated relative enrichment of aromatic compounds during biodegradation. This enrichment significantly correlated with the amount of DOC mineralized suggesting that aromatic compounds were relatively stable and slowly mineralized. 13 C depletion during the incubation of highly degradable DOM solutions indicated an enrichment of lignin-derived aromatic compounds. Py-FI mass spectra indicated increasing contents of phenols and lignin monomers at the expense of lignin dimers and alkylaromatics during incubation. This partial degradation of higher-molecular, lignin-derived DOM compounds was accompanied by relative increases in the proportions of lower-molecular degradation products and microbial metabolites. Carbohydrates, especially when abundant at high initial contents, seem to be the preferred substrate for microorganisms. However, four independent methods suggested also some microbial production of carbohydrates and peptides during DOM degradation. After incubation, the composition of highly degradable DOM samples became similar to relatively stable DOM samples with respect to aromaticity, carbohydrate content, and thermal stability. We conclude that DOM biodegradation seems to result in organic matter properties being a precondition for the formation of stable carbon. These structural changes induced by DOM biodegradation should also result in stronger DOM sorption to the soil matrix additionally affecting DOM stabilization. q 2003 Elsevier Science Ltd. All rights reserved.

Reductive dehalogenation of chlorinated dioxins by an anaerobic bacterium

Abstract: Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs and PCDFs) are among the most notorious environmental pollutants. Some congeners, particularly those with lateral chlorine substitutions at positions 2, 3, 7 and 8, are extremely toxic and carcinogenic to humans. One particularly promising mechanism for the detoxification of PCDDs and PCDFs is microbial reductive dechlorination. So far only a limited number of phylogenetically diverse anaerobic bacteria have been found that couple the reductive dehalogenation of chlorinated compounds--the substitution of a chlorine for a hydrogen atom--to energy conservation and growth in a process called dehalorespiration. Microbial dechlorination of PCDDs occurs in sediments and anaerobic mixed cultures from sediments, but the responsible organisms have not yet been identified or isolated. Here we show the presence of a Dehalococcoides species in four dioxin-dechlorinating enrichment cultures from a freshwater sediment highly contaminated with PCDDs and PCDFs. We also show that the previously described chlorobenzene-dehalorespiring bacterium Dehalococcoides sp. strain CBDB1 (ref. 3) is able to reductively dechlorinate selected dioxin congeners. Reductive dechlorination of 1,2,3,7,8-pentachlorodibenzo-p-dioxin (PeCDD) demonstrates that environmentally significant dioxins are attacked by this bacterium.

The hypoxia-inducible factor-1 alpha is a negative factor for tumor therapy.

Abstract: Tumor hypoxia negatively regulates cell growth and causes a more malignant phenotype by increasing the expression of genes encoding angiogenic, metabolic and metastatic factors. Of clinical importance, insufficient tumor oxygenation affects the efficiency of chemotherapy and radiotherapy by poorly understood mechanisms. The hypoxia-inducible factor (HIF)-1 is a master transcriptional activator of oxygen-regulated genes and HIF-1 is constitutively upregulated in several tumor types. HIF-1 might thus be implicated in tumor therapy resistance. We found that transformed mouse embryonic fibroblasts deficient for HIF-1alpha are more susceptible to the treatment with carboplatin, etoposide and ionizing radiation than wild-type cells. Increased cell death in HIF-1alpha-deficient cells was because of apoptosis and did not involve p53 induction. Tumor chemotherapy of experimental fibrosarcoma in immunocompromised mice with carboplatin and etoposide confirmed the enhanced susceptibility of HIF-1alpha-deficient cells. Agents that did not cause DNA double-strand breaks, such as DNA-synthesis inhibitors or a DNA single-strand break-causing agent equally impaired cell growth, independent of the HIF-1alpha genotype. Functional repair of a fragmented reporter gene was decreased in HIF-1alpha-deficient cells. Thus, hypoxia-independent basal HIF-1alpha expression in tumor cells, as known from untransformed embryonic stem cells, is sufficient to induce target gene expression, probably including DNA double-strand break repair enzymes.

Pop-in effect as homogeneous nucleation of dislocations during nanoindentation

Abstract: Using advanced depth-sensitive hardness measurements, the homogenous nucleation of dislocations has been observed in dislocation-free single crystals This process is related to a sudden displacement jump in the force-displacement curve The mechanical stress for the set-in of this pop-in effect has been estimated with the Hertzian elastic contact theory Experimental results of dislocation loop nucleation show good agreement with the continuum theory of dislocations Electron microscopy provides a direct proof of dislocation nucleation during nanoindentation

Antimicrobial therapy of unexplained fever in neutropenic patients--guidelines of the Infectious Diseases Working Party (AGIHO) of the German Society of Hematology and Oncology (DGHO), Study Group Interventional Therapy of Unexplained Fever, Arbeitsgemeinschaft Supportivmassnahmen in der Onkologie (ASO) of the Deutsche Krebsgesellschaft (DKG-German Cancer Society).

Abstract: Cytostatic chemotherapy of hematological malignancies is often complicated by neutropenia, which increases the risk of infections, especially if the neutrophil count is below 500/microl. Frequently, fever is the first, and in most patients the only, sign of an infection. Unexplained fever is defined as follows: temperature of >/=38.3 degrees C or >/=38.0 degrees C for at least 1 h, or measured twice within 12 h, if the neutrophil count is /=10 days. An empirical mono- or duotherapy with antipseudomonal and antistreptococcal agents should be initiated immediately. In the low risk patient group, oral therapy with cipro-, levo-, or ofloxacin combined with amoxicillin/clavulanic acid is permissible. For standard and high risk patients, monotherapy can be carried out with either ceftazidime, cefepime, piperacillin with tazobactam or a carbapenem. In duotherapy, a single dose of an aminoglycoside is combined with acylaminopenicillin or a cephalosporin of the third or fourth generation. The addition of glycopeptides in empirical therapy should only be considered in the presence of severe mucositis, or if a catheter-associated infection is suspected. If fever persists after 72-96 h of first-line therapy with antibiotics, the regimen should be modified (with the exception of e.g. coagulase-negative staphylococci infections, because these infections take longer to respond). Intermediate risk patients should additionally receive an aminoglycoside after monotherapy (penicillin or a cephalosporin). If a carbapenem was administered for monotherapy, this can be followed by a quinolone and/or a glycopeptide. In the high risk group, the same modifications should be made as in the intermediate risk group but with additional systemic antifungal treatment. In the presence of unexplained fever, fluconazole can be administered at first, but if this fails, amphotericin B (conventional or liposomal), itraconazole, voriconazole or caspofungin should be started. After defervescence to 1000/microl.

Nanophase separation and hindered glass transition in side-chain polymers

Abstract: Nanophase separation on length scales of 1–5 nanometres has been reported previously for small-molecule liquids1, metallic glasses and also for several semicrystalline, liquid-crystalline2,3 and amorphous4 polymers. Here we show that nanophase separation of incompatible main and side-chain parts is a general phenomenon in amorphous side-chain polymers with long alkyl groups. We conclude from X-ray scattering and relaxation spectroscopy data for higher poly(n-alkyl acrylates) (PnAA) and poly(n-alkyl methacrylates) (PnAMA) that alkyl groups of different monomeric units aggregate in the melt and form self-assembled alkyl nanodomains with a typical size of 0.5–2 nm. A comparison with data for other polymer series having alkyl groups reveals that important structural and dynamic aspects are main-chain independent. A polyethylene-like glass transition within the alkyl nanodomains is observed and discussed in the context of a hindered glass transition in self-assembled confinements. This is an interesting link between central questions in glass-transition research and structural aspects in nanophase-separated materials.

Loss of K‐Cl co‐transporter KCC3 causes deafness, neurodegeneration and reduced seizure threshold

Abstract: K-Cl co-transporters are encoded by four homologous genes and may have roles in transepithelial transport and in the regulation of cell volume and cytoplasmic chloride. KCC3, an isoform mutated in the human Anderman syndrome, is expressed in brain, epithelia and other tissues. To investigate the physiological functions of KCC3, we disrupted its gene in mice. This severely impaired cell volume regulation as assessed in renal tubules and neurons, and moderately raised intraneuronal Cl(-) concentration. Kcc3(-/-) mice showed severe motor abnormalities correlating with a progressive neurodegeneration in the peripheral and CNS. Although no spontaneous seizures were observed, Kcc3(-/-) mice displayed reduced seizure threshold and spike-wave complexes on electrocorticograms. These resembled EEG abnormalities in patients with Anderman syndrome. Kcc3(-/-) mice also displayed arterial hypertension and a slowly progressive deafness. KCC3 was expressed in many, but not all cells of the inner ear K(+) recycling pathway. These cells slowly degenerated, as did sensory hair cells. The present mouse model has revealed important cellular and systemic functions of KCC3 and is highly relevant for Anderman syndrome.

Heterozygous mutations of the kinesin KIF21A in congenital fibrosis of the extraocular muscles type 1 (CFEOM1)

Abstract: Congenital fibrosis of the extraocular muscles type 1 (CFEOM1; OMIM #135700) is an autosomal dominant strabismus disorder associated with defects of the oculomotor nerve. We show that individuals with CFEOM1 harbor heterozygous missense mutations in a kinesin motor protein encoded by KIF21A. We identified six different mutations in 44 of 45 probands. The primary mutational hotspots are in the stalk domain, highlighting an important new role for KIF21A and its stalk in the formation of the oculomotor axis.

Plasma atrial natriuretic peptide and brain natriuretic peptide are increased in septic shock: impact of interleukin-6 and sepsis-associated left ventricular dysfunction.

Abstract: Interest has recently focused on the use of neurohormonal markers such as atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) as indices of left ventricular systolic dysfunction and prognosis in heart failure. Also, peptides belonging to the interleukin-6 (IL-6) family have been shown to induce ANP and BNP secretion. We hypothesized that BNP and ANP spillover in the peripheral circulation reflects left ventricular dysfunction and IL-6 production in septic shock. Retrospective, clinical study in the medical intensive care unit of a university hospital. 17 patients with septic shock and 19 control subjects. Collection of clinical and demographic data in relation to ANP, BNP, IL-6, and soluble TNF receptors (sTNF-R-p55, sTNF-R-p75) in plasma over a period of 4 days. In septic shock we found a significant increase in ANP (82.7±9.9 vs. 14.9±1.2 pg/ml) and BNP (12.4±3.6 vs. 5.5±0.7 pg/ml). Plasma ANP peaked together with IL-6. Peaks of ANP and IL-6 were significantly correlated (r=0.73; p<0.01). BNP was inversely correlated to cardiac index (r=–0.56; p<0.05). ANP and BNP increase significantly in patients with septic shock. BNP reflects left ventricular dysfunction. ANP is related to IL-6 production rather than to cardiovascular dysfunction.

Pattern of lymph node metastases in papillary thyroid carcinoma.

Abstract: Background Incidence and pattern of lymph node metastasis (LNM) were evaluated in 35 patients who underwent primary surgery for papillary thyroid carcinoma. Methods Total thyroidectomy with systematic cervicocentral lymphadenectomy was performed routinely. Additionally, 22 patients underwent lymphadenectomy of the ipsilateral cervicolateral compartment. Sternotomy was performed in four patients. Results Primary tumour status was: pT1, n = 7; pT2, n = 12; pT3, n = 4; pT4, n = 12. Twenty-four patients had LNM in the ipsilateral cervicocentral compartment (pT1, n = 2; pT2, n = 8; pT3, n = 4; pT4, n = 10). Nineteen had LNM in the ipsilateral cervicolateral compartment (pT1, n = 4; pT2, n = 6; pT3, n = 2; pT4, n = 7). Contralateral cervicocentral LNM was restricted to patients with pT3 tumours (n = 2) or pT4 tumours (n = 3). No patient had LNM in the contralateral cervicolateral compartment. Only one patient (pT3 tumour) had mediastinal LNM. Conclusion The cervicocentral compartment was most commonly involved with metastases, although the ipsilateral cervicolateral compartment was almost as often affected. In some patients ipsilateral cervicolateral LNM was present in the absence of cervicocentral LNM. Contralateral cervicolateral and upper mediastinal LNM, however, were rare. This study helps to plan radical surgery for papillary thyroid carcinoma. © 1998 British Journal of Surgery Society Ltd

Members of the poly (rC) binding protein family stimulate the activity of the c-myc internal ribosome entry segment in vitro and in vivo.

Abstract: The 5' untranslated region of the proto-oncogene c-myc contains an internal ribosome entry segment and c-Myc translation can be initiated by cap-independent as well as cap-dependent mechanisms. In contrast to the process of cap-dependent initiation, the trans-acting factor requirements for cellular internal ribosome entry are poorly understood. Here, we show that members of the poly (rC) binding protein family, poly (rC) binding protein 1 (PCBP1), poly (rC) binding protein 2 (PCBP2) and hnRNPK were able to activate the IRES in vitro up to threefold when added in combination with upstream of N-ras and unr-interacting protein. The interactions of PCBP1, PCBP2 and hnRNPK with c-myc-IRES-RNA were shown to be specific by ultraviolet crosslinking analysis and electrophoretic mobility shift assays, while immunoprecipitation of the three proteins using specific antibodies followed by reverse transcriptase-polymerase chain reaction showed that they were able to bind c-myc mRNA. c-myc-IRES-mediated translation from the reporter vector was stimulated by cotransfection of plasmids encoding PCBP1, PCBP2 and hnRNPK. Interestingly, the mutated version of the c-myc IRES that is prevalent in patients with multiple myeloma bound hnRNPK more efficiently in vitro and was stimulated by hnRNPK to a greater extent in vivo.