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  • 1
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. Rubredoxin was isolated from the facultative anaerobe Spirochaeta aurantia and from the obligate anaerobe Spirochaeta stenostrepta. The spirochetal rubredoxins contained one atom of iron per molecule and no inorganic sulfide. Their molecular weight (approximately 6000), spectral properties, and amino acid composition resembled those of rubredoxins obtained from anaerobic bacteria. A rubredoxin or a rubredoxin-like protein was present in the host-associated Treponema denticola. Rubredoxin was detected in extracts of both anaerobically- and aerobically-grown cells of S. aurantia. 2. An unstable ferredoxin was isolated from cell extracts of anaerobically-grown S. aurantia, but was not detected in aerobically-grown cells. The spectral characteristics and amino acid composition of this protein were similar to those of other bacterial ferredoxins. Four atoms of iron and four acid-labile sulfide residues were present per molecule. The molecular weight of S. aurantia ferredoxin was near 6000. S. aurantia ferredoxin preparations stimulated the formation of acetyl phosphate from pyruvate by diethylaminoethyl cellulose-treated extracts of Clostridium butyricum, whereas purified spirochetal rubredoxin did not.
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  • 2
    ISSN: 1432-0916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract We extend previous work concerning the construction of unitary scattering amplitudes that correspond to the scattering data at a given energy. The dispersive and absorptive parts are by construction analytic in cosϑ in the small and large Lehmann ellipses, respectively. The dispersive and absorptive parts obtained here, in contrast to those obtained before, are shown to have continuous derivatives on the boundary of their domains of analyticity. The continuum ambiguity in the determination of the scattering amplitude, which is associated with a lack of experimental information on the inelastic contribution to unitarity, is present here as well.
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  • 3
    ISSN: 1432-0916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract We demonstrate the existence of a solution of the nonlinear pion-pion equations that incorporate crossing symmetry, unitarity andl-plane meromorphy. In particular, we show how to guarantee the boundedness of the partial waves ass→∞, even when some Regge trajectories rise beyond unity.
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  • 4
    ISSN: 1432-0916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract When the differential cross-section for spin-zero elastic scattering is given, the elastic unitarity condition constitutes a nonlinear integral equation for the phase of the scattering amplitude. Existence and uniquences theorems for solutions of the equation were obtained by Newton and Martin. Some improvements of the Newton-Martin results on uniqueness and iterative construction of solutions are obtained. Certain details of rigour in the applications of Schauder's theorem by Newton and by Martin are supplied. The case of inelastic spin-zero scattering is treated by adding a term to the unitarity condition to account for absorption. It is shown that in the inelastic region one may have infinitely many different scattering amplitudes with a given differential cross-section. This result is potentially important in phase-shift analysis, since it means that there is a “continuum ambiguity” in the determination of phases and elasticities from scattering data.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 34 (1987), S. 99-101 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract By applying bifurcation theory to a truncated Dyson-Schwinger equation for the quark propagator in massless QCD, we show that dynamical symmetry breaking occurs at a certain critical value of the coupling constant. Essential ingredients are (a) an effective dynamical mass for the gluon, and (b) a running coupling constant.
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  • 6
    ISSN: 1600-0765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Guided tissue regeneration is a clinical procedure used to restore mineralized tissue that has been lost to periodontal disease or after tooth extraction. The procedure makes use of Gore-tex® membranes or Gore-tex® augmentation membranes (GTAM) to prevent migration of keratinocytes and gingival fibroblasts into healing wounds. To begin to characterize the regenerative cells associated with these membranes, human cells have been rescued from membranes retrieved after bone-inductive procedures. Cell lines were established from tissue adherent to Gore-tex® membranes used to regenerate bone around periodontally compromised teeth, and from tissue adherent to GTAM used in edentulous ridge augmentation procedures or in conjunction with implant placement. Cell lines were screened for mineralized nodule formation in vitro prior to their subsequent analysis. All but one of the lines selected for this study formed mineralized nodules in vitro with cells from GTAM tending to form modules more quickly than cells from Gore-tex®. Zymograms and Western blots were used to compare protease profiles of these cells with those of human gingival fibroblasts, keratinocytes and periodontal ligament (PDL) cells. All cell types except for keratinocytes produced a 72 kD protease. In contrast, keratinocytes were the only cells that produced 92 kD gelatinase. In some cell lines, notably those removed from patients after short periods of regeneration, collagenase was the major protease detected on gelatin substrate gels. Some of these cell lines also produced additional proteases including a low molecular weight protease (30 kD) not seen in gingival fibroblasts, PDL cells or keratinocytes.
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  • 7
    ISSN: 1600-0765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The levels of volatile sulphur compounds (VSC) in periodontal pockets and mouth air have been found to correlate with severity of the disease process. The purpose of this study was to examine the influence of hydrogen sulphide and methyl mercaptan on protein metabolism of human gingival fibroblasts. The incorporation of labelled amino acids into protein was used to evaluate effects on total protein content. Changes in collagenous protein concentration were monitored by release of radioactivity following collagenase digestion as well as direct analysis of hydroxyproline. Both thiols were found to reduce total protein synthesis, with mercaptan exerting a greater adverse effect. In cultures exposed to mercaptan, total protein was reduced by 35%. The changes in total protein were accompanied by a corresponding decrease in collagenase-digestible protein. Hydroxyproline analysis of CH3SH-exposed cultures confirmed the changes associated with collagenous proteins. It indicated that in comparison to the controls the CH3SH-exposed cultures had a 70% reduction in collagen which resulted from a combined effect of suppressed synthesis and increased rate of collagen degradation. The possibility of thiol reaction with collagen was determined using in vitro systems in which type I collagen was reacted with varying concentrations of [35S]-H2S. The carboxymethyl (CM) cellulose assays of resulting reaction mixtures indicate that [35S]-radioactivity was incorporated directly into αl, α2, β11, β12 peptide chains. Furthermore, upon exposure of collagen to elevated H2S concentrations, the H2S converted some of the acid-soluble collagen to a more soluble product which could be extracted in neutral salt and analyzed by CM-cellulose chromatography. This effect on collagen solubility may make it more susceptible to enzymatic degradation and contribute to the increased destruction of collagen observed in the thiol-treated fibroblast cultures.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1600-0765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Methyl mercaptan (CH3SH) is a malodorous compound whose levels are elevated in mouth and crevicular air of individuals with active periodontal disease. Since it may play a role in the disease process, its effects were evaluated using human gingival fibroblast cultures and viable porcine unkeratinized oral mucosal tissue sections. Results showed that the protein content of CH3SH-exposed cell cultures pulsed with [14C]-labelled glycine and proline was decreased by approximately 25%. Furthermore, this deleterious effect was irreversible in test cultures subsequently incubated for 24 h in a control 95% air/5% CO2mercaptan-free environment. The supporting slab-gel electrophoresis profiles yielded evidence that exposure to CH3SH caused an alteration in collagen metabolism and a pooling of Type I procollagens. In addition, DNA synthesis was suppressed in CH3SH-exposed cultures by 44.1% at the 24 to 26 h peak of DNA synthesis. This is a true inhibition and not a shift in peak of maximum DNA synthesis as the shape and location of time-course curves of control and test systems is very similar. Proline transport study using [14C]-proline indicated a reduction in proline transport in the range of 40 to 50% in cultures exposed for 24 to 30 h to CH3SH. Significantly even 15 min exposure to 6.7 ng CH3SH/ml of incubating atmosphere suppressed proline transport by approximately 24%). This indicates that even brief exposure to low concentrations of CH3SH has a significant adverse effect on proline transport. Fluorescent staining of tissue sections exposed to mercaptan indicated that the agent elevated the number of cells stained with vital dye. The results demonstrate that CH3SH at concentrations employed in this study significantly decreased total protein content, collagen content, DNA synthesis and proline transport in fibroblast cell cultures, as well as exerting an adverse effect on the cellular integrity of intact oral mucosal tissues.
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  • 9
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] To examine the NK sensitivity of cells during the transformation process, we have constructed vectors that permit controlled expression of c-Ha-ras (Fig. 1). For constitutive expression of ras in fibroblast cells, a 6.6-kilobase (kb) BamHl fragment containing the transforming human c-Ha-ras gene3 ...
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  • 10
    ISSN: 1600-0765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Diabetes mellitus is a systemic disease with profound effects on oral health and periodontal wound healing. Uncontrolled diabetes adversely affects surgical wound healing and is often associated with abnormal proliferation of fibroblasts, excessive angiogenesis and poor bone regeneration. Human gingival fibroblasts and periodontal ligament cells from both diabetics and non-diabetics were evaluated for growth responses following culture in 20 mM glucose, a concentration compatible with blood glucose levels in uncontrolled diabetics. Gingival fibroblasts derived from 9 non-diabetic patients and 3 insulin-dependent diabetics either proliferated or showed little change of growth in elevated glucose. Enhanced proliferation was observed following 1 wk of culture in glucose. Growth of periodontal ligament cells from 5 non-diabetic patients was inhibited by 20 mM glucose. Fibroblasts that were markedly growth stimulated were probed for expression of basic fibroblast growth factor (bFGF) using a reverse-transcribed polymerase chain reaction (RT-PCR). Results indicate that fibroblasts exhibiting the greatest increase in growth in response to high glucose also exhibited increased expression of bFGF. No changes were observed in mRNA expression for platelet-derived growth factor-AA, platelet-derived growth factor-BB, insulin-like growth factor and transforming growth factor-β1. Mitogenic effects induced by the cytosol of fibroblasts exhibiting increases of growth in 20 mM glucose were abrogated by neutralizing antibodies to bFGF. In addition, some periodontal ligament cells that were growth inhibited by high glucose had reduced expression of bFGF. These data suggest that bFGF may play a role in the abnormal wound healing associated with periodontal surgery of uncontrolled diabetics.
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