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  • oxidation  (47)
  • Apoptosis  (46)
  • Springer  (93)
  • American Meteorological Society
  • Elsevier
  • 1995-1999  (93)
  • 1990-1994
  • 1940-1944
  • 1997  (93)
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  • 1995-1999  (93)
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  • 1
    Digitale Medien
    Digitale Medien
    Carbon monoxide electrooxidation on porous Pt–Ru electrodes in sulphuric acid (1997)
    Springer
    Journal of applied electrochemistry 27 (1997), S. 1275-1282 
    Details
    ISSN: 1572-8838
    Schlagwort(e): Carbon monoxide ; Pt-Ru/C catalyst ; Tafel slopes ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract CO electrooxidation on a Pt–Ru/C catalyst was investigated in sulphuric acid electrolyte. The physico-chemical properties of the Pt–Ru/C catalyst were studied by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The influence of temperature, CO partial pressure and proton concentration on the electrochemical oxidation rate was investigated by steady-state galvanostatic polarization measurements. The apparent activation energy decreased from 70 to 30kJmol−1 as the overpotential increased from 0.5 to 0.9V vs NHE. The reaction order with respect to carbon monoxide increased, passing from 0.4 to 1, with the increase of the overpotential from 0.5 to 0.7V vs NHE; a reaction order close to −1 with respect to the protonic concentration was observed, irrespective of the potential. Tafel slopes of about 136mVdec−1 were determined for oxidation of CO and CO/N2 mixtures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1018492122263
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  • 2
    Digitale Medien
    Digitale Medien
    Preparation and characterization of bimodal porous carbons derived from a styrene-divinylbenzene copolymer (1997)
    Springer
    Adsorption 3 (1997), S. 67-79 
    Details
    ISSN: 1572-8757
    Schlagwort(e): porous carbons ; activation ; oxidation ; surface oxygen groups ; LTPD
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract A styrene/divinylbenzene copolymer has been used as precursor for making porous carbons with bimodal pore size distributions (i.e., with both microporosity and mesoporosity). Pretreatment of the as-received copolymer by mild oxidation in air, significantly increased the carbon yield after carbonization. Reactivity studies of the polymer-based chars to CO2 clearly show the influences of some important factors such as carbonization temperature, heating rate, soak time on char reactivities. Bimodal porous carbons were prepared by carbonization of the preoxidized styrene/divinylbenzene copolymer in N2, followed by activation in CO2 at different temperatures to different levels of burnoff. The pore structures of the porous carbons produced have been characterized by various techniques such as gas adsorption and mercury porosimetry. The surfaces of the porous carbons produced, and a commercial carbon adsorbent, have been modified with HNO3 and H2O2 treatment at various conditions. Characterization of the surface oxygen functionality, both quantitatively and qualitatively, has been achieved using techniques such as Linear Temperature Programed Desorption (LTPD) and selective neutralization of bases.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01133008
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  • 3
    Digitale Medien
    Digitale Medien
    The Influence of Catalyst Composition on the Oxidation Process of Carbonado Type Synthesized Polycrystalline Diamonds (1997)
    Springer
    Advanced performance materials 4 (1997), S. 297-304 
    Details
    ISSN: 1572-8765
    Schlagwort(e): carbonado ; diamond ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation of carbonado type synthesized polycrystalline diamonds produced from graphite together with catalytic Ni-Mo alloy doped with TiB2 and BNcub was investigated. It was found that the addition of these boron compounds increases the oxidation resistance of the carbonado type synthesized polycrystalline diamonds. The oxidation mechanism acting on the carbonado type synthesized polycrystalline diamonds and the role of boron compounds in increasing the resistance to the oxygen reaction are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008677105534
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  • 4
    Digitale Medien
    Digitale Medien
    Effect of fluorination of alumina support on activity of platinum catalysts for complete oxidation of benzene (1997)
    Springer
    Catalysis letters 49 (1997), S. 155-161 
    Details
    ISSN: 1572-879X
    Schlagwort(e): fluorination ; alumina ; platinum catalysts ; oxidation ; oxidation of benzene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Platinum supported on fluorinated alumina is more active for the total oxidation of benzene than is the catalyst with the same Pt loading supported on hydrophilic unfluorinated alumina. The Pt-F/alumina catalyst contains well-dispersed small Pt particles, in contrast to Pt/alumina. The high dispersion is a consequence of a strong metal-support interaction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019065507551
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  • 5
    Digitale Medien
    Digitale Medien
    Short-term dynamics in protein and amino acid metabolism (1997)
    Springer
    European journal of nutrition 36 (1997), S. 336-339 
    Details
    ISSN: 1436-6215
    Schlagwort(e): Amino acids ; protein ; metabolism ; meal feeding ; oxidation ; breath test ; Aminosäuren ; Protein ; Stoffwechsel ; Fütterung ; Oxidation ; Atemtest
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die aktuellen Mengen an freien Aminosäuren im Blut reichen nur aus, um die Ganzkörper-Proteinsynthese für einige Minuten aufrecht zu erhalten. Das zeigt, daß die freien Aminosäurenkonzentrationen in der Zirkulation klein und konstant gehalten werden im Vergleich zu den Mengen der Aminosäuren, die täglich aufgenommen und über die Körperproteine umgesetzt werden. Das Verschwinden der Aminosäuren exogenen oder endogenen Ursprungs aus dem freien Aminosäuren-Pool, findet hauptsächlich durch die Proteinsynthese und den Aminosäurenabbau statt. Die Partitionierung der Nahrungs-Aminosäuren zwischen diesen beiden Prozessen im Kurzzeitbereich werden als bedeutsam für die Ökonomie der Ganzkörper-Aminosäuren angesehen. Eine Verbesserung der Aminosäurenökonomie könnte durch solche nutritiven Maßnahmen erreicht werden, welche die Clearance der Nahrungsaminosäuren durch die Proteinsynthese anstelle des Aminosäurenabbaus begünstigen. Diese nutritiven Maßnahmen sollten sich an den „Schwellenwerten“ des Abbaus der individuellen Aminosäuren orientieren.
    Notizen: Summary Actual amounts of free amino acids in the blood are sufficient to support whole body protein synthesis for some minutes only. This indicates that the levels of free amino acids in the circulation are kept small and constant relative to the amounts of amino acids supplied by daily intake and turnover of body proteins. The clearance of the amino acids originating from either endogenous or exogenous sources is mainly due to protein synthesis and metabolic degradation. The partitioning of dietary amino acids between these processes, on the short term, is supposed to play an important role in whole body amino acid economy. Therefore whole body amino acid economy could be improved by nutritional measures that favour the clearance of dietary amino acids by protein synthesis instead of by metabolic degradation. These nutritional measures should to be focused on threshold values for metabolic degradation of individual amino acids.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01617818
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  • 6
    Digitale Medien
    Digitale Medien
    C60: A host lattice for the intercalation of oxygen? (1997)
    Springer
    Microchimica acta 125 (1997), S. 401-406 
    Details
    ISSN: 1436-5073
    Schlagwort(e): fullerenes ; intercalation ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The investigation of structural and electronic properties of the novel family of fullerenes depends on the existence of pure reference materials. Sublimation of the van-der Waals solids is a suitable purification method. Little attention has been paid to the question about the air stability of such sublimed samples in form of crystals or thin films. A combination of thermal desorption spectroscopy, thermal analysis and diffuse reflectance FT-IR spectroscopy is used to show the extent to which oxygen from dry air is intercalated into fullerenes and which detrimental reactivity occurs from attempts to thermally remove („nneal”) air-exposed samples. The conclusion is that any fullerene sample exposed to air will be transformed in part into a polymeric non-fullerene carbon upon thermal treatment to above 400 K irrespective of its initial purity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01246218
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  • 7
    Digitale Medien
    Digitale Medien
    Methane oxidation in soils with different textures and land use (1997)
    Springer
    Nutrient cycling in agroecosystems 49 (1997), S. 91-95 
    Details
    ISSN: 1573-0867
    Schlagwort(e): greenhouse effect ; land use ; methane ; oxidation ; soils
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Intact core samples from soils with different textures and land use were tested for their capacity to oxidise methane. The soil cores were taken from arable land, grassland and forest. It was found that coarse textured soils (6.74–16.38 µg CH4 m-2 h-1) showed a higher methane uptake rate than fine textured soils (4.66–5.34 µg CH4 m-2 h-1). Increasing soil tortuosity was thought to reduce the methane oxidation rate in fine textured soils. The oxidation rate of forest soils (16.32–16.38 µg CH4 m-2 h-1), even with a pH below 4.5, was very pronounced and higher than arable land (11.40–14.47 µg CH4 m-2 h-1) and grassland (6.74–9.30 µg CH4 m-2 h-1). Within the same textural class arable land showed a faster methane uptake rate than grassland. In grassland with a fine texture, even methane production was observed. Nitrogen availability and turnover in these land use systems were thought to cause the different oxidation rates. Decreasing the moisture content slowed down the oxidation rate in all soils. This could be caused by an increased N turnover and a starvation of the methanotrophic bacteria.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009706324386
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  • 8
    Digitale Medien
    Digitale Medien
    The effect of agriculture on methane oxidation in soil (1997)
    Springer
    Nutrient cycling in agroecosystems 49 (1997), S. 59-70 
    Details
    ISSN: 1573-0867
    Schlagwort(e): land use ; methane ; nitrogen fertilizer ; oxidation ; soil
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Aerobic soils are an important sink for methane (CH4) contributing up to 15% of annual global CH4 destruction. However, the sink strength is significantly affected by land management, nitrogen (N) fertilizers and acidity. We tested these effects on samples taken from the Broadbalk Continuous Wheat, Park Grass permanent grassland and Broadbalk and Geescroft Wilderness experiments at Rothamsted. The rates of uptake from the atmosphere of both enhanced (10 ppmv) and ambient (2 ppmv) concentrations of CH4 were measured in laboratory incubations of soil cores under controlled conditions. The most rapid rates of uptake were measured in soil from deciduous woodland at pH 7 (measured in water); acidic (pH 4) woodland soil showed no net CH4 oxidation. While disturbance of the cores used in the experiments did not affect the rate of CH4 uptake, extended (150 years) cultivation of land for arable crops reduced uptake rate by 85% compared to that in the soil under calcareous woodland. The long-term application of ammonium- (NH4) based fertilizer, but not nitrate- (NO3) based fertilizer, completely inhibited CH4 uptake, but the application for the same period of farmyard manure that contained more N than the fertilizer had no inhibitory effect. Although the effects of agricultural practice on the oxidation of CH4 in soil are significant, the differences in oxidation rates between land use types are even greater. The likely effects of forest clearance, agricultural intensification and anthropogenic emissions of CH4 over the last 2500 years have been estimated for the United Kingdom. The calculations indicate that 54% of the current CH4 uptake by UK soils is the result of increased CH4 mixing ratio. They also indicate that land use change has decreased the potential sink strength by 62% or 37 kt CH4 g-1. In countries with much larger land areas than the UK, such as China, aerobic soil is likely to be a more significant factor in calculating net fluxes of CH4. It is important that the impacts of different agricultural managements and land use systems are understood and quantified so that the best possible estimate of CH4 sinks is calculated for comparison with sources.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009704226554
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  • 9
    Digitale Medien
    Digitale Medien
    Effects of Interference and Oxidation on the UV/Visible Rejection Properties of Filters for Soft X-ray Detectors (1997)
    Springer
    Experimental astronomy 7 (1997), S. 51-63 
    Details
    ISSN: 1572-9508
    Schlagwort(e): X-ray ; calibration ; filters ; interference ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report on UV/Visible transmission measurements of aluminum coated Lexan filters designed as UV blocking filters for soft x-ray detectors. Transmission of the filters in the 2300-8000 Å wavelength range is significantly higher than expected. It cannot be accounted for applying a simple slab model of the transmission and adopting material properties reported in the literature. We show that this is due to interference effects which are strongly dependent on the filter geometry, and to oxidation of exposed aluminum surfaces and/or chemical interaction with the plastic support. The results of this work have led to the redesign of the Advanced X-ray Astrophysics Facility High Resolution Camera UV blocking filters.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007919005280
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  • 10
    Digitale Medien
    Digitale Medien
    Autoactivation ofXenopus thyroid hormone receptor β genes correlates with larval epithelial apoptosis and adult cell proliferation (1997)
    Springer
    Journal of biomedical science 4 (1997), S. 9-18 
    Details
    ISSN: 1423-0127
    Schlagwort(e): Thyroid hormone receptor ; Xenopus laevis ; Metamorphosis ; Apoptosis ; Cell proliferation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The thyroid hormone (T3)-dependent amphibian metamorphosis involves degeneration of larval tissues through programmed cell death (apoptosis) and concurrent proliferation and differentiation of adult cell types. As the mediators of the causative effects of T3 on metamorphosis, both thyroid hormone receptor (TR) α and β genes have been found to be expressed in different tissues during this process. In particular, theXenopus TRβ genes have been shown to be regulated by T3 at the transcriptional level and their expression correlates with organ-specific metamorphosis. We demonstrate here by in situ hybridization that theXenopus TRβ genes are regulated in a cell-type specific manner that correlates with tissue transformation. In particular, they are found to be expressed in the larval intestinal epithelial cells prior to their apoptotic degeneration and in the proliferating cells of the adult epithelium, connective tissue, and muscles. However, they are repressed again upon the differentiation of these adult cells. These results implicate that TRβ participates both in inducing apoptosis and stimulating cell proliferation during development.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02255588
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  • 11
    Digitale Medien
    Digitale Medien
    Apoptosis of L1210 leukemia cells induced by 3-deazaadenosine analogs: Differential expression of c-myc, NF-kappa B and molecular events (1997)
    Springer
    Journal of biomedical science 4 (1997), S. 83-90 
    Details
    ISSN: 1423-0127
    Schlagwort(e): Apoptosis ; Cell cycle ; 3-Deazaadenosine analogs ; L1210 lymphocytic leukemia cells ; c-myc ; NF-kappa B
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract A new class of potent apogens (apoptosis-inducing agents) has been identified, consisting of 3-deazaadenosine (DZA), 3-deaza-(±)aristeromycin (DZAri) and 1-β-D-arabinofuranosyl-1H-imidazo[4,5-c]pyridine (ara-3-deazaadenine; DZAra-A). They are inhibitors ofS-adenosylhomocysteine hydrolase and indirect inhibitors of methylation. Furthermore, they have also been found to form 3-deaza-nucleotide analogs. The DZA analogs, DZA, DZAri, and DZAra-A, induced DNA fragmentation in a dose- and time-dependent manner, reaching a maximum at 250 µM after 72 h. Cycloheximide at 0.5 µg/ml completely blocked the DNA fragmentation induced by 250 µM of each of the analogs. Interestingly, exogenous 100 µM L-homocysteine thiolactone abrogated the DNA fragmentation caused by DZAri and DZAra-A, but not by DZA. Flow cytometric analysis showed that DZA arrested the cells in the G2/M phase, whereas the S phase was arrested by DZAri. Correlated with the effect of DZA was a rapid decrease in the expression of c-myc, whereasnur77 and GAPDH were unaffected. In comparison, there was an elevated expression of IFN-γ mRNA without apparent change inbax, p53 or GAPDH mRNA after 24 h. After treatment with DZA, there was an elevated expression of NF-κB DNA binding activity, which became more pronounced at 24 h. Simultaneously, there was an apparent disappearance of AP-1 activity. Thus, DZA most likely inhibited the RNA synthesis of c-myc, a reduction of which could trigger a cascade of gene transcription leading to apoptosis in L1210 cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02255598
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  • 12
    Digitale Medien
    Digitale Medien
    Role of oncogenic transcription factor c-Myc in cell cycle regulation, apoptosis and metabolism (1997)
    Springer
    Journal of biomedical science 4 (1997), S. 269-278 
    Details
    ISSN: 1423-0127
    Schlagwort(e): c-Myc ; Oncogene ; Transcription ; Cancer ; Metabolism ; Apoptosis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Themyc gene was initially discovered as a prototypical retrovirally transduced oncogene. Over the decades, abundant evidence has emerged to support a causal role for the activated cellular gene, c-myc, in animal and human tumors. The gene encodes an oncogenic helix-loop-helix leucine zipper transcription factor that acts as a heterodimer with its partner protein, Max, to activate genes regulating the cell cycle machinery as well as critical metabolic enzymes. The additional ability of c-Myc to repress transcription of differentiation-related genes suggest that c-Myc is a central and key molecular integrator of cell proliferation, differentiation and metabolism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02258350
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  • 13
    Digitale Medien
    Digitale Medien
    Anaerobic ammonia oxidation with nitrogen dioxide by Nitrosomonas eutropha (1997)
    Springer
    Archives of microbiology 167 (1997), S. 106-111 
    Details
    ISSN: 1432-072X
    Schlagwort(e): Key wordsNitrosomonas ; Anaerobic ammonia ; oxidation ; Anaerobic cell growth ; Nitrogen dioxide ; Nitric oxide ; Nitrous oxide ; Dinitrogen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Nitrosomonas eutropha, an obligately lithoautotrophic bacterium, was able to nitrify and denitrify simultaneously under anoxic conditions when gaseous nitrogen dioxide (NO2) was supplemented to the atmosphere. In the presence of gaseous NO2, ammonia was oxidized, nitrite and nitric oxide (NO) were formed, and hydroxylamine occurred as an intermediate. Between 40 and 60% of the produced nitrite was denitrified to dinitrogen (N2). Nitrous oxide (N2O) was shown to be an intermediate of denitrification. Under an N2 atmosphere supplemented with 25 ppm NO2 and 300 ppm CO2, the amount of cell protein increased by 0.87 mg protein per mmol ammonia oxidized, and the cell number of N. eutropha increased by 5.8 × 109 cells per mmol ammonia oxidized. In addition, the ATP and NADH content increased by 4.3 μmol ATP (g protein)–1 and 6.3 μmol NADH (g protein)–1 and was about the same in both anaerobically and aerobically grown cells. Without NO2, the ATP content decreased by 0.7 μmol (g protein)–1, and the NADH content decreased by 1.2 μmol (g protein)–1. NO was shown to inhibit anaerobic ammonia oxidation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002030050422
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  • 14
    Digitale Medien
    Digitale Medien
    Determination of kerogen type by using DSC and TG analysis (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 745-753 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DSC ; kerogen ; oxidation ; pyrolysis ; type determination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The rate of pyrolysis and oxidation of 8 different samples of oil shale kerogen concentrate (KC) were investigated using DSC analysis. Recently performed thermogravimetric studies (TG and DTG) with the same samples of KC indicated that the activation energy of the pyrolysis of specific KCs increases with increasing paraffinic structure in the KC. An opposite effect, i.e. a decrease of the activation energy with an increase of paraffinic structure was determined in the case of KC oxidation. In this study, using the standard ASTM E-698 method based on the determined temperature at which the maximum heat effect could be observed (exo in the case of oxidation and endo in the case of pyrolysis), an activation energy for the pyrolysis, as well as for the oxidation process was determined and also successfully correlated with the content of paraffinic structure of KC. Thus, the higher content of paraffinic structure in KCs indicates that higher values of the activation energy could be determined either in the case of pyrolysis or oxidation followed by DSC analysis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01996758
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  • 15
    Digitale Medien
    Digitale Medien
    Using isothermal microcalorimetry for the prediction and testing of long-term properties of materials and products (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 1017-1023 
    Details
    ISSN: 1572-8943
    Schlagwort(e): degradation ; microcalorimetry ; moisture ; oxidation ; permeability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The use of isothermal microcalorimetry (MC) as a sensitive monitor for slow reactions is demonstrated in a number of examples. In Example 1 the spontaneous decomposition of a nitrate ester propellant is studied and the absolute degradation rate estimated. Example 2 illustrates how MC can be used for comparing the rate of oxidative ageing at different O2 concentrations. Synergetic effects between oxygen and moisture in accelerated ageing of nitrile rubber are evaluated from a so-called 4-point test in Example 3. The last example shows a simple MC technique for rapid determination of moisture permeability through a polymeric sealant.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01996789
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  • 16
    Digitale Medien
    Digitale Medien
    Thermal properties and reactivity determination of micro- and submicrometer nickel powders (1997)
    Springer
    Journal of thermal analysis and calorimetry 48 (1997), S. 657-664 
    Details
    ISSN: 1572-8943
    Schlagwort(e): nickel powders ; oxidation ; thermal analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Monodispersed fine metal nickel powders of uniform shape and high purity are increasingly required for specific uses in many technological areas, especially in the preparation of electronic materials such as the manufacture of conductive inks and pastes and the formation of catalysts. Metallic nickel powders were prepared in ethylene glycol by the reduction of a nickel solution. Hydrazine was used as a reducing agent. Metal powders were characterized by chemical analysis, scanning electron microscopy (SEM), thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). Particle size distributions were determined using laser light scattering. The reactivity and purity of these fine nickel powders were tested by repeated oxidation and reduction of nickel powders in oxidative and reductive atmospheres.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01979511
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  • 17
    Digitale Medien
    Digitale Medien
    Thermogravimetric studies of the synthesis of cas from gypsum, CaSo4·2H2O and phosphogypsum (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 1501-1507 
    Details
    ISSN: 1572-8943
    Schlagwort(e): calcium sulphide ; gypsum ; oxidation ; phosphogypsum ; reduction ; stability ; thermogravimetry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Using a heating rate of 2°C min−1, CaS reacts with oxygen in air from 700°C to form CaSO4, with a complete conversion at 1100°C. Synthesis of CaS from the reaction between CaSO4 containing compounds and carbon compounds in air would not be possible, as the carbon reacts from 600°C with oxygen in the air to give CO2. Heating stoichiometric amounts of carbon and pure CaSO4, synthetic gypsum or phosphogypsum in a nitrogen atmosphere, results in the formation of CaS from 850°C. Using a heating rate of 10°C min−1, the formation of CaS is completed at 1080°C. Addition of 5% Fe2O3 as a catalyst lowers the starting temperature of the reaction to 750°C. Activation energy values at different fraction reaction values (α) differ between 340 and 400 kJ mol−1. The relationship between the activation energy values and conversion (α) indicates that the reaction proceeds via multiple steps.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01983709
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  • 18
    Digitale Medien
    Digitale Medien
    Low/high temperature relationships in dinitramide salts by DEA/DSC and study of oxidation of aluminum powders by DSC/TG (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 1161-1170 
    Details
    ISSN: 1572-8943
    Schlagwort(e): basicity ; dinitramides ; kinetics ; oxidation ; tanδ ; transition temperatures
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The dinitramide salts of ammonia (ADN), hexamethylenetetramine (HDN), potassium (KDN), and sodium (NaDN) showed a linear relationship between the DSC rate of decomposition at the peak maximum and the DEA tanδ value at the low temperature transition peak. As the cation basicity increased in the series ADN〈HDN〈KDN〈NaDN, there was an increase in the low temperature transition peak, the energy barrier for relaxation, and the decomposition peak temperature, and a decrease in the tanδ value at the low temperature transition peak, specific heat capacity, and the rate and enthalpy of decomposition. The more basic salts were more thermally stable (i.e., higher decomposition temperature) and less energetic (i.e., lower enthalpy of decomposition). The more internal free volume (disorder) present in these salts, the higher the rates of relaxation and decomposition. Five aluminum powders of different surface areas were analyzed by DSC in platinum sample pans, and it was found that the enthalpy and rate of oxidation increased as the particle size of Al decreased while the enthalpy of the Al melt decreased. TG showed a two-step weight gain in the oxidation of Al with plateaus in the 650 and 1130°C regions and the percent weight gain increased as the particle size of Al decreased. Variable DSC and TG heating rate studies showed that the activation energies for the first step in the oxidation process increased as the particle size of Al increased.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01983671
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  • 19
    Digitale Medien
    Digitale Medien
    Oxidation behavior of several chromia-forming commercial nickel-base superalloys (1997)
    Springer
    Oxidation of metals 47 (1997), S. 381-410 
    Details
    ISSN: 1573-4889
    Schlagwort(e): Ni-Base superalloys ; Astroloy ; Waspaloy ; Udimet 720 ; oxidation ; chromia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Several commercially available Ni-base superalloys were exposed isothermally in air at temperatures between 750° and 1000°C and also under cyclic conditions at 1000°C. The kinetics of oxidation were determined and the scales were analyzed by electron microscopy and X-ray diffraction. Thin adherent chromia-rich scales formed on the alloys at 750°C after 1000 hr. Although Waspaloy showed the lowest weight gain in this test, it also showed the deepest internal corrosion due to oxidation of the grain-boundary carbides. At temperatures up to 1000°C the external scales were also chromia-rich but there was greater internal corrosion. Titanium in the alloys oxidized, diffusing through the chromia scale to form faceted rutile (TiO2) grains at the surface as well as forming TiO2 and TiN internally. The amount of rutile at the oxide surface increased with temperature and alloy Ti concentration. Alumina formed as discrete internal oxides below the chromia scale, although Astroloy when oxidized isothermally at 1000°C developed a semicontinuous internal layer of alumina due to its higher Al content. Under cyclic conditions Astroloy formed a thicker, less-protective scale of transition oxides probably due to its lower Cr content.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02134783
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  • 20
    Digitale Medien
    Digitale Medien
    Oxidation behavior of an Fe-38Ni-13Co-4.7Nb-1.5Ti-0.4Si superalloy at high temperature in Ar-H2O atmospheres (1997)
    Springer
    Oxidation of metals 47 (1997), S. 411-426 
    Details
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; Incoloy 909 ; superalloy ; scale ; high temperature ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation of an Fe-38Ni-13Co-4.7Nb-1.5Ti-0.4Si superalloy (Incoloy 909 type alloy), was investigated at temperatures between 1000 K and 1400 K in Ar-(1, 10%)H20 atmosphere using metallographic, electron probe microanalysis, and X-ray diffraction techniques. The oxide scales consist of an external scale and an internal scale which has an intergranular scale (above 1200 K) and an intergranular scale. The oxide phases in each scale are identified asα-Fe2,O3 (below 1200 K) or FeO (above 1300 K) and CoO · Fe2O3 and FeO · Nb2O5, respectively. The morphologies, the oxide phases and the oxidation rates do not depend on the partial pressure of H2O in the range between one and ten percent in Ar gas. The rate constants for the intergranular-scale formation in this alloy are about one-tenth as large as those in Fe-36%Ni alloy reported previously. At all the temperatures the scales grow according to a parabolic rate law and the apparent activation energies for the processes are estimated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02134784
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  • 21
    Digitale Medien
    Digitale Medien
    Water-vapor-effect on the oxidation of Fe-21.5 wt.%Cr-5.6 wt.%Al at 1000°C (1997)
    Springer
    Oxidation of metals 47 (1997), S. 445-464 
    Details
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; Fe-Cr-Al alloy ; water vapor ; ESCA ; RHEED
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Fe-21.5 wt. %Cr-5.6 wt. %Al oxidation, at 1000°C, in dry or wet oxygen shows that steam has an influence on the oxide-scale growth mechanism. Steam modifies the kinetics of early-stage oxidation. In dry oxygen, an initial fast linear regime is observed during one hour. Under wet conditions, weight-gain curves follow the same parabolic regime over the entire oxidation test. The scale structure strongly depends on the presence of steam in the gaseous environment. With dry oxygen, the scale is composed mainly ofα-Al2O3 after the initial formation ofγ-Al2O3 identified by ESCA and RHEED. The kinetics transient stage corresponds to the necessary time for the internal part of the initialγ-Al2O3 scale to transform into a continuousα-Al2O3 diffusion barrier. Under wet oxygen conditions, transient oxides are identified as (Mg, Fe) (Cr, Al)2O4, MgAl2O4 (orthorhombic), Al2O3 (hexagonal), these oxides transform into MgAl2O4 (cubic), Cr3O4, Fe2O3,α-Al2O3, with time. When water vapor does not change drastically oxidation kinetics, the induced presence of iron and chromium in the oxide scale could be responsible for weakening the protectiveness of alumina scales.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02134786
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  • 22
    Digitale Medien
    Digitale Medien
    The transient state in the oxidation of binary alloys forming the most-stable oxide: A numerical solution (1997)
    Springer
    Oxidation of metals 47 (1997), S. 507-524 
    Details
    ISSN: 1573-4889
    Schlagwort(e): alloys ; high temperature ; oxidation ; transient state
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The initial transient high-temperature oxidation stage for binary alloys forming the most-stable oxide has been examined by means of a numerical procedure based on the finite-difference method. At variance with previous models, the present treatment takes into account the effect of the rate of the reaction at the scale/gas interface over the corrosion kinetics. The calculations concerning the transient stage are developed either using the general parabolic rate law to represent the overall scaling kinetics or using the rate law of the reaction at the scale/gas interface as a boundary condition without imposing any particular rate law to the overall process. A correct analysis of the oxidation behavior of binary alloys during the transient stage must take into account the kinetics effect of the rate of the surface reaction. The concentration of the most-reactive element at the alloy/scale interface changes regularly with time, decreasing gradually from the initial bulk value to its final steady-state value. The present results are in good agreement with those obtained by means of an approximate analytical model developed previously.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02134789
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  • 23
    Digitale Medien
    Digitale Medien
    An approximate treatment of the transient state in the oxidation of binary alloys forming the most-stable oxide. Part II: Single-phase alloys in systems with a solubility gap (1997)
    Springer
    Oxidation of metals 47 (1997), S. 525-550 
    Details
    ISSN: 1573-4889
    Schlagwort(e): high temperatures ; oxidation ; transient state
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The transient state in the oxidation of solid solutions of a most-noble componentA in a most-reactive componentB (beta phase) for binaryA-B alloys presenting a limited reciprocal solubility of the two metals has been examined assuming that theirB content is sufficient for the exclusive growth of externalBO scales. Above a criticalB content of the alloy theBO scales may grow directly on the surface of the beta phase, while below this limit they can only form over a layer ofB-depleted solid solution ofB inA (alpha phase), which appears after a critical time. An approximate analytical expression for the profile of concentration ofB in the alloy has been adopted to calculate the flux ofB in the metal. Moreover, the effect of the reaction between the gas and the external oxide surface has been taken into account using a procedure developed by Wagner for the oxidation of pure metals. The corrosion kinetics as well as all the parameters involved, such as the concentration ofB at the alloy-scale interface, have been calculated as functions of the corrosion time. The results show that, as time proceeds, the instantaneous parabolic rate constant increases and the concentration ofB at the alloy-scale interface decreases, both tending gradually to their corresponding steady-state values. It is also predicted that if the rate of transformation of the beta phase in the alpha phase after the alloy reaches the composition of equilibrium at the interface with the oxide is lower than the corresponding rate of displacement of the alloy surface due to scale growth, the corrosion of beta phase alloys may eventually lead to the formation of two phase mixtures of alpha phase andBO which are expected to grow at much larger rates than in the presence of a uniform continuous alpha layer.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02134790
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  • 24
    Digitale Medien
    Digitale Medien
    Evolution of oxides on Ni-base ODS superalloys (1997)
    Springer
    Oxidation of metals 48 (1997), S. 1-39 
    Details
    ISSN: 1573-4889
    Schlagwort(e): Ni-base ODS superalloys ; oxidation ; initial stages of oxidation ; alumina ; chromia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Mechanically-alloyed Ni-base ODS superalloys currently receive attention for application in future gas turbines because they exhibit outstanding mechanical properties at high temperatures. They also protect themselves against oxidation by forming chromia and/or alumina scales. However, little attention has been given so far to the initial stages of oxidation of Ni-base ODS superalloys, containing Cr as well as Al in considerable amounts. In the current work, oxidation at 1150°C was studied for different holding times up to 200 hr for the commercial materials MA6000 and PM3030 which contain. Al in increasing amounts. MA 754, a chromia former, was investigated as a reference. It was shown that for the potential alumina formers MA6000 and PM3030 the continuity and therefore protectiveness of the secondary Al2O3 at later stages is indeed determined by the initial stages of oxidation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01675260
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  • 25
    Digitale Medien
    Digitale Medien
    Decarburization and internal oxidation in a commercial-grade nickel (1997)
    Springer
    Oxidation of metals 48 (1997), S. 129-141 
    Details
    ISSN: 1573-4889
    Schlagwort(e): decarburization ; nickel ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract A commercial-grade nickel containing small amounts of carbon, manganese, and silicon was exposed to air for periods up to 288 hr at 1050°C to study the effect of oxidation on the formation of oxides of these impurity elements. Exposure of nickel to air led to decarburization. The maximum amount of decarburization occurred during the initial period of air exposure and the loss in carbon was more in the metal with a smaller section size. Decarburization in the metal produced voids in the oxide scale due to the formation of CO2 gas. It has been shown further that CO and/or CO2 gas bubbles, which form in high purity nickel on grain boundaries during exposure to air at elevated temperatures, cannot exist in commercial-grade nickel where manganese is present as an impurity. Instead, oxides of manganese form in the grain boundaries as well as in the matrix. This is because manganese oxide is more stable than CO or CO2 gas.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01675265
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  • 26
    Digitale Medien
    Digitale Medien
    On the oxidation ofα-Fe andε-Fe2N1−z : I. Oxidation kinetics and microstructural evolution of the oxide and nitride layers (1997)
    Springer
    Oxidation of metals 48 (1997), S. 87-109 
    Details
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; kinetics ; iron ; iron-nitride
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation of α-Fe and ɛ-Fe2N1−z at 573 K and 673 K in O2 at 1 atm was investigated by thermogravimetrical analysis, X-ray diffraction, light-optical microscopy, scanning electron microscopy and electron probe X-ray microanalysis. Upon oxidation at 573 K and 673 K, on α-Fe initially α-Fe2O3 develops, whereas on ɛ-Fe2N1−z initially Fe3O4 develops. In an early stage of oxidation the oxidation rate of ɛ-Fe2N1−z appears to be much larger than of α-Fe. This can be attributed largely to an effective surface area available for oxygen uptake, which is much larger for ɛ-Fe2N1−z than for α-Fe due to the porous structure of ɛ-Fe2N1−z as prepared by gaseous nitriding of iron. The development of a magnetite layer in-between the hematite layer and the α-Fe substrate, at a later stage of oxidation, enhances layer-growth kinetics. After 100 min oxidation at 673 K the (parabolic) oxidation rates for α-Fe and ɛ-Fe2N1−z become about equal, indicating that on both substrates the oxide growth is controlled by the same rate limiting step which is attributed to short-circuit diffusion of iron cations. Oxidizing ɛ-Fe2N1−z increases the nitrogen concentration in the remaining ɛ-iron nitride, because the outward flux of iron cations, necessary for oxide growth, leads to an accumulation of nitrogen atoms left behind.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01675263
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  • 27
    Digitale Medien
    Digitale Medien
    Effect of niobium additions on CO2-enhanced oxidation of titanium-aluminum intermetallic alloys (1997)
    Springer
    Oxidation of metals 48 (1997), S. 201-214 
    Details
    ISSN: 1573-4889
    Schlagwort(e): titanium-aluminum alloys ; niobium ; intermetallics ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract In a recent study, CO2 has been reported to enhance the oxidation rate of binary titanium-aluminum alloys. The detrimental effect of CO2 was not, however, observed in a ternary alloy containing niobium. In this paper, possible explanations for these observations are examined. First, results from the literature regarding the effects of niobium in improving the resistance of titanium-aluminum alloys are briefly reviewed. Second, a thermodynamic analysis which offers a possible explanation for the beneficial effect of niobium in eliminating the CO2-enhanced oxidation of titanium-aluminum alloys is presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01670499
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  • 28
    Digitale Medien
    Digitale Medien
    The effect of nanocrystallization on the selective oxidation and adhesion of Al2O3 scales (1997)
    Springer
    Oxidation of metals 48 (1997), S. 215-224 
    Details
    ISSN: 1573-4889
    Schlagwort(e): nanocrystallization ; oxidation ; mechanism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Many mechanisms for the effect of reactive elements on the selective oxidation and scale adhesion of alloys have been proposed. However, nanocrystallization (or microcrystallization) has recently been found to have almost the same effect as that of reactive elements. This note reviews the effect of nanocrystallization on the selective oxidation and adhesion of Al2O3 scale with particular reference to the author's own results.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01670500
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  • 29
    Digitale Medien
    Digitale Medien
    High-temperature oxidation of pure titanium in CO2 and Ar-10%CO2 atmospheres (1997)
    Springer
    Oxidation of metals 48 (1997), S. 289-302 
    Details
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; titanium ; rutile ; scale ; high temperature ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation behavior of pure titanium has been investigated in the temperature range of 1000 K to 1300 K in CO2 or Ar-10%CO2. Optical microscopy, electron probe microanalyses, and X-ray measurements on the oxide scales formed during oxidation indicate that their structures are nearly independent of temperature and the corrosion atmosphere. The scales consisted of two layers, an external one and an internal one, having a rutile (TiO2) structure. The parabolic rate law was confirmed for growth of the external scale and the permeation depth of oxygen in titanium with apparent activation energies of 266 and 226 kJ/mol, respectively. The rate-determining diffusion species in the oxidation processes are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01670504
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  • 30
    Digitale Medien
    Digitale Medien
    Phase analysis by variable-incidence X-ray diffraction: Application to zirconium oxidation (1997)
    Springer
    Oxidation of metals 48 (1997), S. 329-345 
    Details
    ISSN: 1573-4889
    Schlagwort(e): zirconium ; X-ray diffraction ; oxidation ; phase analysis ; texture
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation of zirconium at high temperature (T〉 400°C) leads to reaction products of two allotropic oxide (ZrO2 monoclinic and ZrO2 tetragonal). The distribution and proportion of these two phases were studied as a function of time and space by X-ray diffraction techniques. Quantitative analyses are possible after some corrections, and we demonstrate the presence of a phase gradient in the oxide scale. The interest of this nondestructive method is then discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01670506
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  • 31
    Digitale Medien
    Digitale Medien
    The air oxidation of two-phase Cu-Cr alloys at 700–900°C (1997)
    Springer
    Oxidation of metals 48 (1997), S. 357-380 
    Details
    ISSN: 1573-4889
    Schlagwort(e): chromium ; copper ; binary alloys ; two-phase alloys ; oxidation ; high temperatures
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation in air of three two phase Cu-Cr alloys with nominal Cr contents of 25, 50, and 75 wt. % was studied at 700–900°C. The alloys corroded nearly parabolically, except at 900°C, when the corrosion rates decreased with time more rapidly than predicted by the parabolic rate law. The corrosion rate decreased for higher Cr contents in the alloy under constant temperature and generally increased with temperature for the same alloy composition. The scales were complex and consisted in most cases of an outermost copper oxide layer free from chromium and an inner layer composed of a matrix of copper oxide or of the double oxide Cu2Cr2O4, often containing particles of chromium metal surrounded by chromia and then by the double oxide. Metallic copper was also frequently mixed with chromia. Cr-rich regions tended to form continuous chromia layers at the base of the scale, especially at the highest temperature. No chromium depletion was observed in the alloy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02153456
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  • 32
    Digitale Medien
    Digitale Medien
    Influence of ceria coatings on growth stresses developed in wüstite scales formed on pure iron at 800°C (1997)
    Springer
    Oxidation of metals 48 (1997), S. 417-438 
    Details
    ISSN: 1573-4889
    Schlagwort(e): iron ; oxidation ; CeO2 coating ; in situ ; growth stress ; residual stress ; texture ; X ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract In situ XRD stress determinations have been performed during oxidation of pure iron (p(O2=2 × 10−3 Pa,T=800°C)). The compressive stress, initially present in the substrate due to surface preparation, is completely released at 400°C. Under the test conditions, the in situ compressive-stress level determined in the FeO scale during oxidation is not strongly dependent upon the presence of a ceria coating. On blank and coated specimens, the compressive stress varies from −400 ± 80 MPa to −150 ± 100 MPa during 30 hr oxidation. The decrease is quicker at the beginning of the test performed on blank specimens. Epitaxial relationships between the wüstite scale and iron (under low-pressure starting conditions) caused thein situ compressive stress in the oxide scale to be two times greater compared to the usual test conditions. This indicates that epitaxial relationships can be a source of stress in an oxide scale that ceria coatings may lower compressive stresses.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02153459
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  • 33
    Digitale Medien
    Digitale Medien
    Chloridation-oxidation of Fe-Cr and Ni-Cr alloys at 800°C (1997)
    Springer
    Oxidation of metals 48 (1997), S. 527-551 
    Details
    ISSN: 1573-4889
    Schlagwort(e): chloridation ; oxidation ; Fe-Cr alloys ; Ni-Cr alloys
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The chloridation-oxidation behavior of Fe-Cr (0–25 wt. %Cr) and Ni-Cr (0–20 wt.%Cr) alloys was studied at 800°C in three different H2-HCl-H2O(ν) environments. In a low-HCI and low-H2O(ν) environment, where Cr2O3 is thermodynamically stable, the corrosion resistance of the Fe-Cr alloys increased with increasing Cr content in the alloys. In a high-HCl and high-H2O(ν) environment, where FeCr2O4 is stable and CrCl2 is metastable, the corrosion resistance of the Fe-Cr alloys depended similarly on the Cr content. Low-Cr-Fe-Cr alloys exhibited large weight losses, while Fe-Cr alloys with higher than 19 wt. %Cr showed good corrosion resistance. In an environment of high-HCl in the absence of H2O(ν), the evaporative corrosion rate was fast and limited by gas phase diffusion, and independent of the Cr content in the Fe-Cr alloys. Ni and Ni-Cr alloys generally showed good corrosion resistance in the environments of high H2O(ν) because of the low NiCl2 vapor pressure and formation of a protective Cr2O3 scale. However, in the environment of high HCl in the absence of H2O(ν), selective formation and evaporation of CrCl2 occur, which results in Cr depletion and networks of voids for even a high-Cr Ni-Cr alloy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02153464
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  • 34
    Digitale Medien
    Digitale Medien
    Chloridation-oxidation of nine commercial high-temperature alloys at 800°C (1997)
    Springer
    Oxidation of metals 48 (1997), S. 553-596 
    Details
    ISSN: 1573-4889
    Schlagwort(e): chloridation ; oxidation ; HCl ; high-temperature alloys ; high-temperature corrosion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Chloridation-oxidation studies of nine commercial high-temperature alloys were carried out at 800°C in three different H2-HCl-H2O(ν) environments: (A) both low HCl and H2O(ν) partial pressures, where either Cr2O3 or FeCr2O4 is stable, (B) both high HCl and H2O(ν) partial pressures, where FeCrO4 is stable and CrCl2 is metastable, and (C) high HCl partial pressure in the absence of H2O(ν), where either CrCl2 or Cr2O3 is stable. Although alloy 600 has the lowest Cr content of these nine alloys, it showed excellent corrosion resistance in all three environments because of its high Ni content. Alloy 304, with the lowest Ni content of the nine alloys, exhibited poor corrosion resistance in the environment C, fair resistance in the environment B and good resistance in the environment A. Alloy 800 showed very good resistance in Environment A, and fair corrosion resistance in Environment B; however, it suffered linear weight-loss kinetics when exposed to Environment C The alloys 617, 214, HR-160, X, 230 and 86 have good corrosion resistance in Environments A and B because of their relatively high contents of oxide-scale-forming elements Cr and/or Al. In Environment C, chlorine dramatically decreased the adhesion of the scale on the surface, and aluminum in alloys 617 and 214 hardly showed its usual beneficial effect in combating corrosion, nor does silicon in alloy HR-160. Different corrosion mechanisms are proposed for the alloys in the different environments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02153465
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  • 35
    Digitale Medien
    Digitale Medien
    An approximate treatment of the transient state in the corrosion of binary alloys forming the most-stable oxide. Part I: Solid-solution alloys (1997)
    Springer
    Oxidation of metals 47 (1997), S. 91-115 
    Details
    ISSN: 1573-4889
    Schlagwort(e): binary alloys ; oxidation ; transient state ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The initial transient stage in the oxidation of binary alloys forming scales exclusively composed of the most stable oxide is examined by means of a simplified approach which avoids the numerical integration of the diffusion equation for the transport of the metal components in the alloy. At variance with previous solutions to this problem obtained by means of numerical methods, this treatment takes into account also the effect of the gas-scale reaction at the outer surface of the oxide. The concentration of the most-reactive component at the alloy surface changes gradually with time from the initial bulk value towards the corresponding steady-state value without involving any minimum, while the overall rate of the reaction presents a gradual transition from an initial nearly linear towards final parabolic behavior.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01682373
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  • 36
    Digitale Medien
    Digitale Medien
    Oxidation resistance of sputtered Ni3(AlCr) nanocrystalline coating (1997)
    Springer
    Oxidation of metals 47 (1997), S. 247-258 
    Details
    ISSN: 1573-4889
    Schlagwort(e): Ni3Al-base alloy ; sputtering ; nanocrystalline coating ; oxidation ; scale adhesion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Isothermal and cyclic oxidation resistance at 1000°C in air were investigated for a cast Cr-containing Ni3Al-base alloy and its sputtered nanocrystalline coating. The results indicated that both the cast Ni3Al alloy and its sputtered coating exhibit excellent isothermal oxidation resistance as a result of the formation of Al2O3 scales. However, the cast alloy possesses very poor cyclic oxidation resistance because of the spallation of the initially formed Al2O3 scale during cooling and subsequent formation of NiO. On the contrary, the sputtered Ni3(AlCr) nanocrystalline coating exhibits very good cyclic oxidation resistance due to the significant improvement of the adhesion of Al2O3.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01668513
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  • 37
    Digitale Medien
    Digitale Medien
    Prevention of lens protein glycation by taurine (1997)
    Springer
    Molecular and cellular biochemistry 177 (1997), S. 245-250 
    Details
    ISSN: 1573-4919
    Schlagwort(e): cataract ; crystalline ; glycation ; oxidation ; taurine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Modifications in lens protein structure and function due to nonenzymic glycosylation and oxidation have been suggested to play a significant role in the pathogenesis of sugar and senile cataracts. The glycation reaction involves an initial Schiff base formation between the protein NH2 groups and the carbonyl group of a reducing sugar. The Schiff base then undergoes several structural modifications, via some oxidative reactions involving oxygen free radicals. Hence certain endogenous tissue components that may inhibit the formation of protein-sugar adduct formation may have a sparing effect against the cataractogenic effects of sugars and reactive oxygen. The eye lens is endowed with significant concentration of taurine, a sulfonated amino acid, and its precursor hypotaurine. It is hypothesized that taurine and hypotaurine may have this purported function of protecting the lens proteins against glycation and subsequent denaturation, in addition to their other functions. The results presented herein suggest that these compounds are indeed capable of protecting glycation competitively by forming Schiff bases with sugar carbonyls, and thereby preventing the glycation of lens proteins per se. In addition, they appear to prevent oxidative damage by scavenging hydroxyl radicals. This was apparent by their preventive effect against the formation of the thiobarbituric acid reactive material generated from deoxy-ribose, when the later was exposed to hydroxyl radicals generated by the action of xanthine oxidase on hypoxanthine in presence of iron.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006863322454
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  • 38
    Digitale Medien
    Digitale Medien
    Sol-Gel Coatings on Metals (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 443-449 
    Details
    ISSN: 1573-4846
    Schlagwort(e): coatings ; protection of metals ; oxidation ; corrosion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Sol-gel derived films can be deposited on metals to improve their resistance to oxidation and corrosion or to modify their surface properties. However, practical applications are limited by problems intrinsic to sol-gel processing or specific of coating/metal systems. Coatings aimed to improve oxidation and wet corrosion resistance have been the most studied. The results published in the literature show that sol-gel coatings may offer good protection against oxidation. More difficult is to achieve a protection against wet corrosion. An important aspect of the application of the sol-gel method for coating metallic objects is also the deposition technique.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1018373404815
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  • 39
    Digitale Medien
    Digitale Medien
    Sol-gel coatings on metals (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 443-449 
    Details
    ISSN: 1573-4846
    Schlagwort(e): coatings ; protection of metals ; oxidation ; corrosion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Sol-gel derived films can be deposited on metals to improve their resistance to oxidation and corrosion or to modify their surface properties. However, practical applications are limited by problems intrinsic to sol-gel processing or specific of coating/metal systems. Coatings aimed to improve oxidation and wet corrosion resistance have been the most studied. The results published in the literature show that sol-gel coatings may offer good protection against oxidation. More difficult is to achieve a protection against wet corrosion. An important aspect of the application of the sol-gel method for coating metallic objects is also the deposition technique.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02436880
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  • 40
    Digitale Medien
    Digitale Medien
    The air oxidation of two-phase Cu-Ag alloys at 650–750°C (1997)
    Springer
    Oxidation of metals 47 (1997), S. 21-52 
    Details
    ISSN: 1573-4889
    Schlagwort(e): copper ; silver ; high temperature ; oxidation ; two-phase alloys
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The corrosion of three two phase Cu-Ag alloys containing 25, 50, and 75 wt% Ag has been studied at 650 and 750°C. In all cases the alloys formed external scales of copper oxides. At the same time, an internal precipitation of Cu2O within a silver matrix was also produced, with an oxide volume fraction larger for the alloys richer in Cu. Beneath this mixed layer a region of single-phase solid solution of Cu in silver formed for Cu-50Ag and especially for Cu-75Ag. Silver metal remained in the metal-consumption zone, acting essentially as an inert marker, except for a few particles with were incorporated into the growing scales. Both pure Cu and the alloys corroded parabolically, but the rate constants for the alloys decreased with increased Ag content under constant temperature. The various aspects of the corrosion of these alloys are examined by taking into account the possible effects associated with the presence of two metal phases.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01682370
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  • 41
    Digitale Medien
    Digitale Medien
    Identification of diffusing species and the dynamic nature of diffusion paths during oxidation of a dilute Ni-Cr alloy (1997)
    Springer
    Oxidation of metals 47 (1997), S. 69-89 
    Details
    ISSN: 1573-4889
    Schlagwort(e): duplex-layer formation ; dynamic oxygen-diffusion path ; Ni-Cr alloy ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The results of an investigation of oxidation of a Ni-1 at.% Cr alloy are presented. Photolithographic marker experiments revealed that the markers were found to reside at the interface between a predominantly columnar outer NiO layer and a very fine grain inner layer of NiO, indicating that substantial oxygen ingress had occurred through the columnar scale. New oxide growth at the metal-oxide interface requires the oxidant to be transported across the oxide layer. Since the measured diffusion rate of oxygen ions along grain boundaries and through the lattice is much too slow to account for the observed microstructural growth (∼1: 1 ratio of inner and outer layers), it is necessary to postulate that the oxidant traverses the scale along some type of short-circuit path other than grain boundaries. Extensive formation of elongated pores and pipelike channels was observed along columnar oxide grain boundaries. Thus, it appears that the transport of oxygen occurs via voids (pores) formed by vacancy coalescence at the columnar grain boundaries. These pores appear to open and close continuously. Formation of new fine-grained oxide in these pores was observed to have sometimes completely resealed the void, suggesting a dynamic nature of the voids.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01682372
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  • 42
    Digitale Medien
    Digitale Medien
    Oxidation of the intermetallics MoSi2 and TiSi2—A comparison (1997)
    Springer
    Oxidation of metals 47 (1997), S. 139-203 
    Details
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; MoSi2 ; TiSi2 ; air ; oxygen ; O and Si transport in SiO2
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation behavior of two MoSi2 variants, one Mo-rich and one Si-rich, and TiSi2 was investigated between 1000 and 1400°C in air, oxygen and an 80/20-Ar/O2 mixture. A protective SiO2 scale develops on MoSi2 in all atmospheres in the temperature range investigated. The SiO2 modification changes around 1300°C from tridymite to cristobalite. This change in SiO2 modification seems to cause an enhanced formation of SiO2 and evaporation of MoO3. The SiO2 grows at the MoSi2-scale interface. In air a two-layer scale grows on TiSi2 between about 1000 and 1200°C with an inner inwards growing fine-grain mixture of SiO2 + TiO2 and an outer outward-growing TiO2 partial layer. TiN formation in the transient oxidation is responsible for the formation of the inner mixed partial layer because in N -free atmospheres a scale of a SiO2 matrix with some Ti oxide precipitates inside is formed. A one-layer scale structure similar as that in N-free atmosphere is found on TiSi2 in air at T 〉 1200°C. In oxygen the TiO2 precipitates grow as needles mostly oriented perpendicular to the surface. Due to the faster oxygen transport in TiO2 compared with SiO2, these TiO2 needles act as “oxygen pipes,” causing an enhanced oxidation of TiSi2 in front of these needles. The SiO2 scale dissolves about 1–2% TiO2. This doping causes a mixed oxygenand Si transport with the consequence that the SiO2 scale on TiSi2 grows partly by oxygen transport inwards and Si transport outwards. The SiO2 modification is cristobalite over the entire temperature range investigated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01682375
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  • 43
    Digitale Medien
    Digitale Medien
    The steady-state corrosion kinetics of single-phase binary alloys with a solubility gap forming the most-stable oxide (1997)
    Springer
    Oxidation of metals 47 (1997), S. 215-235 
    Details
    ISSN: 1573-4889
    Schlagwort(e): high temperature ; oxidation ; binary alloys ; steady-state
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The steady-state, high-temperature oxidation kinetics of single phase alloys rich in a most-reactive componentB in binaryA-B systems presenting a limited solubility of the two components (beta phase alloys) have been examined assuming the exclusive formation of the most-stable oxideBO v. Alloys sufficiently rich inB can form externalBO v scales directly in contact with the beta phase, while below a criticalB content the growth ofBO v involves also the appearance of an intermediate layer ofB-depleted solid solution ofB inA (alpha phase). The parabolic rate constants for the oxidation of single-phase beta alloys are lower than those of alloys of identicalB content which are single-phase over the whole range of composition (solid-solution alloys) but higher than for two-phase alpha + beta alloys under the same values of all the relevant parameters. Moreover, the tendency of single-phase beta alloys to form the most-stable oxide simultaneously as an external scale and internally to the alloy is greater than for solid-solution alloys but smaller than for two-phase alloys.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01668511
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  • 44
    Digitale Medien
    Digitale Medien
    High-temperature oxidation behavior of laser-surface-alloyed incoloy-800H with Al (1997)
    Springer
    Oxidation of metals 47 (1997), S. 259-275 
    Details
    ISSN: 1573-4889
    Schlagwort(e): laser surface alloying ; aluminum ; superalloys ; oxidation ; microstructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The high-temperature oxidation resistance of laser-surface-alloyed Incoloy 800H with Al has been investigated. Several samples have been exposed to 1000°C in air and subsequently analyzed by optical microscopy, SEM, and electron microprobe X-ray fluorescence spectroscopy in order to determine their microstructure and composition. The results show that the laser-treated materials have a considerably higher oxidation resistance than the nontreated materials due to the formation of an Al-rich layer close to the surface, which acts as a barrier against oxygen diffusion into the bulk.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01668514
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  • 45
    Digitale Medien
    Digitale Medien
    Role of the Mitochondrial Permeability Transition Pore in Apoptosis (1997)
    Springer
    Bioscience reports 17 (1997), S. 67-76 
    Details
    ISSN: 1573-4935
    Schlagwort(e): Apoptosis ; necrosis ; mitochondria ; megachannel ; permeability transition ; programmed cell death ; poteases
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Mitochondrial permeability transition (PT) involves the formation of proteaceous, regulated pores, probably by apposition of inner and outer mitochondrial membrane proteins which cooperate to form the mitochondrial megachannel (=mitochondrial PT pore). PT has important metabolic consequences, namely the collapse of the mitochondrial transmembrane potential, uncoupling of the respiratory chain, hyperproduction of superoxide anions, disruption of mitochondrial biogenesis, outflow of matrix calcium and glutathione, and release of soluble intermembrane proteins. Recent evidence suggests that PT is a critical, rate limiting event of apoptosis (programmed cell death): (i) induction of PT suffices to cause apoptosis; (ii) one of the immediate consequences of PT, disruption of the mitochondrial transmembrane potential (ΔΨm), is a constant feature of early apoptosis; (iii) prevention of PT impedes the ΔΨm collapse as well as all other features of apoptosis at the levels of the cytoplasma, the nucleus, and the plasma membrane; (iv) PT is modulated by members of the apoptosis-regulatory bcl-2 gene family. Recent data suggest that the acquisition of the apoptotic phenotype, including characteristic changes in nuclear morphology and biochemistry (chromatin condensation and DNA fragmentation), depends on the action of apoptogenic proteins released from the mitochondrial intermembrane space.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1027339418683
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  • 46
    Digitale Medien
    Digitale Medien
    Oxidative Damage and Fragmentation of Mitochondrial DNA in Cellular Apoptosis (1997)
    Springer
    Bioscience reports 17 (1997), S. 237-250 
    Details
    ISSN: 1573-4935
    Schlagwort(e): Apoptosis ; DNA fragmentation ; mitochondrial DNA ; oxidative damage
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The molecular genetics and bioenergetics of oxidative damage, fragmentation, and fragility of mitochondrial DNA in cellular apoptosis is reviewed in connection with the “redox mechanism of ageing”.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1027324410022
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  • 47
    Digitale Medien
    Digitale Medien
    Effects of postnatal age and of thymectomy on hamster pulmonary neuroendocrine system and aspects of programmed cell death (1997)
    Springer
    Cell & tissue research 290 (1997), S. 553-567 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words. Neuroendocrine system ; Lung ; Neuroepithelial bodies ; Apoptosis ; Thymectomy ; Golden hamster
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Effects of postnatal age and neonatal thymectomy on the numbers and characteristics of pulmonary neuroepithelial bodies (NEB) were investigated in 14-day- compared with 2.5-month-old hamsters. Left lung sections were stained for the marker PGP 9.5 and used for light-microscopic quantification, while the right lungs were processed for an electron-microscopic survey of the NEB ultrastructural features. For the first time, it is clearly demonstrated that, depending on the sampling method, the number of NEB may rise or fall with age; when considering the entire lung volume, the actual number of NEB doubles, whereas when studying a constant surface area, their number apparently decreases. Also, the proportion of alveolar NEB as well as luminal contact increase on normal development. In neonates, in contrast to older animals, apoptosis is clearly present in NEB, and approximately 10% of the NEB are associated with inflammatory cells. In some cases, the dead cells have properties of both apoptosis, disintegration and cytoplasmic degeneration. The presence of intracorpuscular neutrophilic granulocytes correlates with cellular death and innervation of the NEB. Thymectomy causes only minor effects on the pulmonary neuroendocrine system. It is argued that development of the NEB and of their innervation continue during the postnatal period.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050961
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  • 48
    Digitale Medien
    Digitale Medien
    Programmed cell death of plant tracheary elements differentiating in vitro (1997)
    Springer
    Protoplasma 196 (1997), S. 197-211 
    Details
    ISSN: 1615-6102
    Schlagwort(e): Apoptosis ; Programmed cell death ; Tracheary element ; Xylogenesis ; Zinnia elegans
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We used various microscopic and labeling techniques to examine events occurring during the programmed cell death (PCD) of plant tracheary elements (TEs) developing in vitro. TEs differentiating in vitro synthesize a secondary cell wall which is complex in composition and pattern at approximately 72 h after hormone manipulation. The timing of PCD events was established relative to this developmental marker. Cytoplasmic streaming continues throughout secondary wall synthesis, which takes 6 h to complete in a typical cell. Vital dye staining and ultrastructural analysis show that the vacuole and plasma membrane are intact during secondary cell wall synthesis, but the cytoplasm becomes less dense in appearance, most likely through the action of confined hydrolysis by small vacuoles which are seen throughout the cell at this time. The final, preeminent step of TE PCD is a rapid collapse of the vacuole occurring after completion of secondary cell wall synthesis. Vacuole collapse is an irreversible commitment to death which results in the immediate cessation of cytoplasmic streaming and leads to the complete degradation of cellular contents, which is probably accomplished by release of hydrolytic enzymes sequestered in the vacuole. This event represents a novel form of PCD. The degradation of nuclear DNA is detectable by TUNEL, an in situ labeling method, and appears to occur near or after vacuole collapse. Our observations indicate that the process of cellular degradation that produces the hollow TE cell corpse is an active and cell-autonomous process which is distinguishable morphologically and kinetically from necrosis. Although TE PCD does not resemble apoptosis morphologically, we describe the production of spherical protoplast fragments by cultured cells that resemble apoptotic bodies but which are not involved in TE PCD. We also present evidence that, unlike the hypersensitive response (HR), TE PCD does not involve an oxidative burst. While this evidence does not exclude a role for reactive oxygen intermediates in TE PCD, it does suggest TE PCD is mechanistically distinct from cell death during the HR.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01279568
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  • 49
    Digitale Medien
    Digitale Medien
    A structural analysis of cytoskeleton components during the execution phase of apoptosis (1997)
    Springer
    Protoplasma 198 (1997), S. 163-169 
    Details
    ISSN: 1615-6102
    Schlagwort(e): Actin ; Actin-binding proteins ; Apoptosis ; F9 embryonal carcinoma cells
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary During the execution phase of apoptosis, the cell undergoes a set of morphological changes which reveal the activation of a complex machinery leading the cell to its disruption into small, spherical, membrane-bounded fragments called apoptotic bodies. In the present study, we have focused on the implications of the micro-filament network in the early stages of the active phase of apoptosis. By using confocal microscopy, we have analysed the location of the actin microfilaments and two actin-binding proteins, α-actinin and myosin, in F9 embryonal carcinoma cells undergoing apoptosis during the stages previous to their fragmentation. Our results show that these proteins locate in the centre of the disrupting cell and form a three-dimensional structure which suggests the existence of a fully functional contractile system involved in the fragmentation of the cell and the formation of apoptotic bodies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01287565
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  • 50
    Digitale Medien
    Digitale Medien
    Etoposide phosphate, the water soluble prodrug of etoposide (1997)
    Springer
    Pharmacy world & science 19 (1997), S. 119-125 
    Details
    ISSN: 1573-739X
    Schlagwort(e): Apoptosis ; Chemotherapy ; Drug resistence ; Necrosis ; P53 tumor suppressor gene ; Programmed cell death
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Apoptosis, or programmed cell death, is an orderly and genetically controlled form of cell death. In a morphological sense, it differs from necrosis in that cellular shrinkage and chromatin condensation occurs, followed by fragmentation of nuclear components within membrane-bound vesicles which are cleared by phagocytosis without damage to adjacent tissue. The molecular pathway includes an initiating phase, which starts after signalling by external triggers, such as ligation to distinct receptors or by endogenous mechanisms related to aging or to exogenous irreversible cellular or nuclear damage. The initiation phase is followed by a decision phase. During this phase transduction occurs of the apoptotic signal to nuclear and cytoplasmatic target enzymes, which includes activation of endonucleases and enzymatic alterations of the cytoskeleton. There are numerous proteins and lipid–derived moieties which modulate the apoptotic mechanism in positive or negative direction. The execution phase is started when the cell has arrived at a stage of no return. The nuclear DNA is cleaved into multiples of 180–200 basepairs, the plasma membrane integrity and the mitochondria remain initially intact, the cell splits up into apoptotic bodies, small vesicles which enclose the nuclear and cellular remnants. Finally, the clearing phase is arrived, when the apoptotic bodies are phagocytosed by adjacent cells and macrophages. It is thought that the pharmacodynamics of anticancer drugs consists of two distinct steps. The first step includes the interaction with its cellular target, which is not lethal per se. The commitment of the cell to undergo apoptosis forms the second step. The efficacy of anticancer drugs is determined by the ability to selectively sensitize tumor cells to apoptosis, which depends to a large extent from the expression of various oncogenes, such as bcl–2, p53, bax, ras, c–myc and others, and from endogenous factors. It is a challenge in pharmacological research to explore apoptosis by modulating the extrinsic and intrinsic regulators in a positive or negative direction in order to improve the efficacy of anticancer treatment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008654316572
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  • 51
    Digitale Medien
    Digitale Medien
    Apoptosis and mammary gland involution: reviewing the process (1997)
    Springer
    Apoptosis 2 (1997), S. 19-24 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; bcl-2 gene family ; hormones ; mammary gland involution ; proteinase ; tissue remodelling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Apoptosis is a process of programmed cell death. Mammary gland involution is a tissue remodelling process. Mammary epithelial cell apoptosis is an integral component of tissue remodelling but it is only one element. Equally important are the factors which degrade basement membrane and extracellular matrix. Both operations are required for completion of mammary gland involution. The primary apoptotic process occurs first and is temporally distinct from the second stage of involution typified by lobular-alveolar collapse. Local factors related to milk accumulation trigger the first stage, but loss of systemic hormonal stimulation governs the second stage. Changes in the expression patterns of cell cycle control genes and bcl-2 family member genes are found in the first stage. Proteinase gene activation dominates the second stage. These findings support a two stage model of mammary gland involution. Both mammary epithelial cell apoptosis and mammary gland remodelling advance through a process which includes both loss of survival factors and gain of death factors. This review focuses on signalling pathways and genetic controls which are activated and repressed during mammary gland involution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026454207398
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  • 52
    Digitale Medien
    Digitale Medien
    HIV-gp120 induced cell death in hematopoietic progenitor CD34+ cells (1997)
    Springer
    Apoptosis 2 (1997), S. 61-68 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; bone marrow ; cord blood ; CD34+CD4+ cells ; fas antigen ; HIV-1 infection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Haematologic abnormalities accompany the majority of HIV-1 infections. At present it is unclear whether this is due directly to HIV infection of hematopoietic progenitor cells, or whether this results from an indirect mechanism secondary to HIV infection. Here we provide evidence for an indirect mechanism, whereby hematopoietic progenitor cells undergo HIV gp120-induced apoptosis (programmed cell death) even in the absence of HIV infection. Freshly isolated, purified human hematopoietic progenitor CD34+ cells, derived from both umbilical cord blood and bone marrow, co-expressed the CD4 marker at low density on their surface. Although these CD34+CD4+ cells theoretically should be capable of productive infection by HIV, we found that HIV-IIIB could not establish productive infection in these cells. Nonetheless, gp120 from IIIB could bind the cells. Thus, binding of gp120 did not correlate with infectivity. Furthermore, binding of gp120 was a specific event, leading to apoptosis upon crosslinking with anti-gp120 through a fas-dependent mechanism. If apoptosis is also observed in vivo even in uninfected hematopoietic cells, this could contribute significantly to the impairment in hematopoietic cell number and function. Our data suggest a novel indirect mechanism for depletion of CD34+ and CD34+-derived cells even in the absence of productive viral infection of these cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026439726053
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  • 53
    Digitale Medien
    Digitale Medien
    HIV-1 envelope glycoproteins-mediated apoptosis is regulated by CD4 dependent and independent mechanisms (1997)
    Springer
    Apoptosis 2 (1997), S. 47-60 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; CD4 ; HIV ; PMA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The progressive loss of CD4 T lymphocytes is one of the hallmarks of HIV infection. The reverse correlation observed in vivo, between plasmatic HIV levels and CD4 T lymphocyte counts, supports the concept that direct HIV-mediated cell death contributes to this depletion. Previously, we and others have demonstrated, in vitro, that interactions between membrane-expressed HIV-envelope glycoprotein complexes and CD4 ecto-molecules are critical to cell killing which occurs mainly by apoptosis. Here, by the use of a co-culture model, in which chronically HIV-1 infected cells trigger apoptosis in uninfected CD4+ target cells, we have investigated the role of different CD4 domains in HIV envelope-mediated apoptosis. Target cells were A201 lymphoblastoid cell lines expressing wild-type CD4 or mutant forms of CD4. We show that the cytoplasmic domain of CD4 was not required for apoptosis induction. In contrast, the HIV permissive cell line expressing a CD4/CD8 chimeric molecule which contains only the first 171 amino acids of CD4, appeared to be resistant to HIV-induced apoptosis; thus suggesting that the D3-D4 CD4 module plays somewhat a regulatory role. Pre-treatment of wild-type CD4 expressing target cells by the phorbol ester PMA which leads to down-regulation of CD4, completely abolished apoptosis. Interestingly, in cells expressing CD4 devoid of its cytoplasmic domain, PMA blocked partially cell death without affecting, as expected, the CD4 expression. Taken together, these results demonstrate that although CD4 expression is essential for HIV envelope induced apoptosis, the apoptotic signal could be delivered in the absence of its cytoplasmic domain. Consistent with this, we suggest that other membrane associated molecule(s) are recruited for the signalling to initiate apoptosis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026435625144
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  • 54
    Digitale Medien
    Digitale Medien
    Serum withdrawal and etoposide induce apoptosis in human lung carcinoma cell line A549 via distinct pathways (1997)
    Springer
    Apoptosis 2 (1997), S. 199-206 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; ERK ; JNK ; p53 ; Rb
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The molecular events associated with apoptosis induced by two distinct triggers (1) serum withdrawal and (2) etoposide treatment were investigated in the human lung carcinoma cell line A549. Although both serum withdrawal and etoposide treatment resulted in internucleosomal DNA fragmentation, the morphologic features were distinct. Serum deprived apoptotic cells appeared small, round and refractile, with little evidence of nuclear fragmentation; etoposide-induced apoptotic cells appeared enlarged and flattened and displayed prominent nuclear fragmentation. p53 and p21/waf1 protein levels were elevated in etoposide-treated cells, but not in cells subjected to serum with-drawal. Apoptosis induced by both treatments was accompanied by a significant reduction in Rb protein levels. However, etoposide treatment led to hypo-phosphorylation of Rb, while serum withdrawal did not alter the Rb phosphorylation pattern. Serum withdrawal-induced apoptosis was correlated with activation of JNK and suppression of ERK activities, while both JNK and ERK activities were slightly elevated during etoposid- induced apoptosis. Together, these results support the hypothesis that apoptosis induced by serum withdrawal and etoposide treatment occurs through different pathways and involves distinct mediators.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026420616484
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  • 55
    Digitale Medien
    Digitale Medien
    Apoptotic and necrotic cell death are both induced by electroporation in HL60 human promyeloid leukaemia cells (1997)
    Springer
    Apoptosis 2 (1997), S. 330-336 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; electroporation ; HL-60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Cell death was induced by electroporation in HL60 cells, a human promyeloid leukaemia strain, in order to determine by both morphological and biochemical criteria whether necrotic or apoptotic processes occurred. Cells sampled at several times after electroporation were analyzed for the assessment of the following end-points: (i) chromosomal DNA fragmentation; (ii) cell viability; (iii) mono- and oligonucleosomes in the cytoplasmic fraction; (iv) apoptotic index; and (v) morphology of treated cells. The results indicate that about 50% of the cells killed by electroporation die through necrosis, while the remaining 50% of the cells undergo apoptosis. Chromosome damage was also studied by cytogenetic analysis at metaphase. The possibility of killing tumour cells by electroporation, as a variant of electrotherapy, constitutes, in our opinion, a promising procedure in cancer therapy, avoiding the undesirable side effects normally derived from treatment with cytotoxic drugs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026497306006
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  • 56
    Digitale Medien
    Digitale Medien
    Apoptosis induced by cadmium (1997)
    Springer
    Apoptosis 2 (1997), S. 359-367 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; cadmium ; metallothionein ; superoxide ; zinc-finger
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Cell death resulting from cadmium (Cd) intoxication has been confirmed to occur through apoptosis by morphological and biochemical studies. However it is still not clear whether Cd itself or metallothionein (MT) induced by Cd is the major factor responsible for the apoptosis. Although apoptosis is inducible by exposure of cells to various stimuli, the common pathway involved is generally accepted to be activation of endonucleases that induce internucleosomal cleavage of DNA, resulting in the ‘ladder’ formation observed upon agarose gel electrophoresis and the chromatin condensation seen by electron microscopy. Cd does not seem to activate the endonuclease in vitro. However, Cd itself can be associated with apoptosis through indirect oxidative stress by inhibition of antioxidant enzymes and possible interaction with zinc finger protein. In addition to the direct effect of Cd, MT appears to play dual roles in apoptosis induction: one as a Cd carrier by which Cd accumulates in the nucleus, and the other as an inhibitor of zinc finger proteins, which include transcriptional factors related to apoptosis such as the product of the apoptosis resistance gene A20. In this review, we demonstrated that the mode of cell death following Cd exposure is associated with intracellular movement of Cd and MT. A possible mechanism for Cd-induced apoptosis is also discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026401506914
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  • 57
    Digitale Medien
    Digitale Medien
    Apoptosis induced in L1210 leukaemia cells by an inhibitor of the chymotrypsin-like activity of the proteasome (1997)
    Springer
    Apoptosis 2 (1997), S. 455-462 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; experimental cancer therapy ; L1210 leukaemia ; proteasome ; proteasome inhibitor ; TNF
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Of a number of factors involved in apoptosis, protease activity may play a crucial role. We show that N-benzyloxycarbonyl-Ile-Glu( O-t-butyl)-Ala-leucinal (PSI), a selective inhibitor of the chymotrypsin-like activity of the proteasome, induces massive apoptosis in murine leukaemia L1210 cells. At 50 nM concentration, PSI induces a block of cytokinesis, while higher concentrations (500 nM) cause S phase block and massive apoptosis. Z-Leu-leucinal, a specific calpain inhibitor, did not induce apoptosis. In contrast to previous reports, TNF-α did not enhance apoptosis when combined with PSI. Our results suggest that proteasome inhibitors may be considered as potential anti-neoplastic agents.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026470027387
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  • 58
    Digitale Medien
    Digitale Medien
    Expression of Bax, Bcl-2, Waf-1, and PCNA gene products in an immortalized human endothelial cell line undergoing p53-mediated apoptosis (1997)
    Springer
    Apoptosis 2 (1997), S. 442-454 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; endothelial ; p53
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Transfection of the wild-type p53 gene into an immortalized human endothelial cell line (ECV-304) by recombinant adenoviral delivery resulted in high level expression of the wild-type p53 protein and induction of apoptosis. Increases in the number of apoptotic cells were observed within 12 h after infection of ECV-304 cells with recombinant p53 adenovirus, as deter-mined by the appearance of internucleosomal DNA fragmentation ladders and by TUNEL and electron microscopic analyses. Control cells infected with a β-galactosidase recombinant adenovirus exhibited little or no increase in apoptosis over uninfected cells. The expression of Waf-1 and Bax gene products were in-creased substantially in apoptotic ECV-304 cells as determined by Northern blot, reverse transcription-PCR and immunoblotting analyses. Lesser increases in the expression of the PCNA gene were detected in ECV-304 cells undergoing apoptosis. Both control and apoptotic ECV-304 cells did not express detectable levels of Bcl-2 mRNA or protein in Northern blotting and immunoblotting analyses, respectively. The data suggest a role for the Bax gene product in p53-mediated apoptosis of endothelial cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026418010549
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  • 59
    Digitale Medien
    Digitale Medien
    Life and death decisions: the role of the IAPs in modulating programmed cell death (1997)
    Springer
    Apoptosis 2 (1997), S. 423-441 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; IAP ; NAIP ; TNF
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Multicellular organisms have evolved elaborate signal transduction pathways for maintaining homeostasis through the control of cell proliferation and death. The recent surge of interest in the regulation of programmed cell death has led to the rapid identification of many proteins involved in controlling and executing apoptosis. The inhibitors of apoptosis proteins (IAPs) constitute a family of highly conserved death suppressing proteins that were first identified in baculoviruses, and that has recently expanded to include at least two homologues in Drosophila melanogaster and four in rodents and humans. In this article we review the current state of IAP research. Two of the IAPs, HIAP-1 and HIAP-2, have been placed within the TNFα induced cell death pathway which involves two receptors for TNFα and multiple, overlapping signal transduction proteins. A third, X-linked gene termed XIAP, is ubiquitously expressed and appears to have a broad range of suppressor activity to a variety of apoptotic triggers. The fourth member, NAIP, has been identified as the protein product of a candidate gene for the inherited neuromuscular disorder, spinal muscular atrophy (SMA). The neuroprotective activity of NAIP in an in vivo model of cerebral ischemia has also been demonstrated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026465926478
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  • 60
    Digitale Medien
    Digitale Medien
    Effects of BCL-2 overexpression on the sensitivity of MCF-7 breast cancer cells to ricin, diphtheria and Pseudomonas toxin and immunotoxins (1997)
    Springer
    Apoptosis 2 (1997), S. 192-198 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; cancer therapy ; drug resistance ; LMB-7
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Immunotoxins are presently being evaluated as novel agents for cancer therapy. The direct mechanism by which immunotoxins kill cancer cells is inhibition of protein synthesis, but cytotoxicity due to induction of apoptosis has also been observed with these agents. Some cancers that express high levels of BCL-2 are relatively resistant to apoptosis inducing agents. It is therefore important to determine to what degree the toxicity of ricin, diphtheria toxin, Pseudomonas exotoxin and Pseudomonas exotoxin derived immunotoxins towards cancer cells can be attributed to inhibition of protein synthesis, and to what degree to subsequent induction of apoptosis. We compared the sensitivity of MCF-7 breast cancer cells that were stably transfected with a BCL-2 expression plasmid and thus protected against apoptosis and of MCF-7 cells transfected with a control plasmid towards ricin, diphtheria and Pseudomonas toxin, a Pseudomonas toxin-derived immunotoxin (LMB-7) and tumour necrosis factor α (TNF). We found that BCL-2 mediated inhibition of apoptosis renders the cells almost completely resistant (1000-fold) to tumour necrosis factor, but the same cells were only 3–10 fold more resistant to cytotoxicity induced by immunotoxin LMB-7 as well as Pseudo-monas exotoxin, diphtheria toxin and ricin. We next studied several leukaemia cell lines with variable levels of BCL-2 expression and found them quite sensitive to a Pseudomonas exotoxin containing immunotoxin independent of the level of BCL-2. Our data indicate that although BCL-2 overexpression can have a modest effect on sensitivity to an immunotoxin, cell lines derived from patients are still very sensitive to immunotoxins.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026468532413
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  • 61
    Digitale Medien
    Digitale Medien
    Therapy for oral squamous cell carcinoma by tegafur and streptococcal agent OK-432 in combination with radiotherapy: Association of the therapeutic effect with differentiation and apoptosis in the cancer cells (1997)
    Springer
    Apoptosis 2 (1997), S. 227-238 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; differentiation ; OK-432 ; oral squamous cell carcinoma ; radiotherapy ; tegafur
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Twenty patients with oral squamous cell carcinoma having mainly stage II or III lesions without distant metastasis, were treated with tegafur and streptococcal agent, OK-432, in combination with radiotherapy. As a consequence, 16 cases among the treated 20 cases showed complete remission by this therapy alone. Especially, we have found that the squamous cell carcinoma arising in non-keratinizing oral epithelium rather than in keratinizing oral epithelium has better response to this therapy. Among the 16 cases with complete remission (CR) by the current therapy, 10 cases were histopathologically diagnosed as well-differentiated squamous cell carcinoma and six cases as moderately differentiated squamous cell carcinoma. When we examined immunohistochemically the expres-sion of various antigens such as proliferating cell nuclear antigen (PCNA), p53 and LeY or the presence of DNA fragmentation by nick-end labelling in the biopsy materials taken at the first visit to our clinic from 20 patients treated with the current therapy, the CR group showed a significantly increased LeY expres-sion level ( p〈 0.05) and DNA fragmentation rate ( p〈 0.05) as compared with the partial response (PR, n= 3) + no change (NC, n= 1) group. On the other hand, the CR group with respect to PCNA expression level was significantly decreased as compared with the PR + NC group ( p〈 0.05). From these findings, it can be considered that the therapy for oral squamous cell carcinoma by UFT and OK-432 in combination with radiotherapy is very effective, which may be associated with differentiation or apoptosis in oral squamous carcinoma cells. In addition, we present the clinical findings and results of immunohistochemical staining for the biopsy materials obtained from four CR cases treated with the current therapeutic method.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026428918301
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  • 62
    Digitale Medien
    Digitale Medien
    Role of apoptosis and apoptosis-related proteins in the cisplatin-resistant phenotype of human tumor cell lines (1997)
    Springer
    Apoptosis 2 (1997), S. 540-548 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; bcl-2 ; cisplatin resistance ; p53
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Since apoptosis is the primary mode of cell death induced by cisplatin, the role of apoptosis and apoptosis-related gene products in cisplatin resistance was investigated in four human cisplatin-resistant cell lines of different tumour type. A common feature of the resistant sublines was a reduced susceptibility to drug-induced apoptosis compared to parental sensitive lines. Loss of wild-type p53 function was not a general event associated with the development of drug resistance. An increased bcl-2 expression was found in resistant cells characterized by mutant p53 (A431/Pt and IGROV-1/Pt), whereas in osteosarcoma (U2-OS/Pt) and in ovarian carcinoma (A2780/CP) cells with wild-type p53, bcl-2 levels were markedly reduced. U2-OS/Pt cells had a 16-fold increase in the level of Bcl-xL protein. Stable transfection of U2-OS cells with bcl-xL cDNA conferred a low level of drug resistance to cisplatin, suggesting that overexpression of this gene contributes to the ci splatin-resistant phenotype of this osteosarcoma cell system. In conclusion, these observations suggest a variable contribution of apoptosis-related genes to cisplatin resistance depending on the biological background of the cell system and presumably reflecting different pathways of apoptosis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026442716000
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  • 63
    Digitale Medien
    Digitale Medien
    A C-terminal domain of HIV-1 accessory protein Vpr is involved in penetration, mitochondrial dysfunction and apoptosis of human CD4+ lymphocytes (1997)
    Springer
    Apoptosis 2 (1997), S. 69-76 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; CD4+ lymphocytes ; cell penetration ; HIV-1 ; mitochondrial dysfunction ; Vpr
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract We have previously shown that expression of HIV-1 vpr in yeast results in cell growth arrest and structural defects, and identified a C-terminal domain of Vpr as being responsible for these effects in yeast.1 In this report we show that recombinant Vpr and C-terminal peptides of Vpr containing the conserved sequence HFRIGCRHSRIG caused permeabilization of CD4+ T lymphocytes, a dramatic reduction of mitochondrial membrane potential and finally cell death. Vpr and Vpr peptides containing the conserved sequence rapidly penetrated cells, co-localized with the DNA, and caused increased granularity and formation of dense apoptotic bodies. The above results suggest that Vpr treated cells undergo apoptosis and this was confirmed by demonstration of DNA fragmentation by the highly sensitive TUNEL assay. Our results, together with the demonstration of extracellular Vpr in HIV infected individuals,2,3 suggest the possibility that extracellular Vpr could contribute to the apoptotic death and depletion of bystander cells in lymphoid tissues4,5 during HIV infection.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026487609215
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  • 64
    Digitale Medien
    Digitale Medien
    The restrictive proteolysis of α-fodrin to a 120 kDa fragment is not catalyzed by calpains during thymic apoptosis (1997)
    Springer
    Apoptosis 2 (1997), S. 84-90 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; α-fodrin ; calpain ; thymocytes ; x-irradiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The α-subunit (240 kDa) of fodrin was found to be digested selectively to a 120 kDa fragment during apoptosis of rat thymocytes in vivo and in vitro. This fragment was detected by an antibody (Ab) against full length α-fodrin, but not by the anti-N-terminal sequence (GMMPR) of the μ-calpain-generated 150 kDa fragment Ab or the anti-PEST sequence of α-fodrin Ab. On the other hand, basal levels of the 150 kDa fragment were constantly recognized by these three antibodies during apoptosis. The production of the 120 kDa fragment during apoptosis was not affected by the addition of calpain inhibitors such as Ac-LLLnal and E-64d, despite inhibition of the generation of the 150 kDa fragment. When x-irradiated thymocytes were incubated in the presence of N-tosyl-L-phenylalanyl chloromethyl ketone (TPCK), both production of the 120 kDa fragment and apoptosis were suppressed. Purified μ- and m-calpain did not catalyze the formation of the 120 kDa fragment from purified α-fodrin in vitro. These results suggest that a protease different from calpains is involved in the major process of α-fodrin proteolysis to a 120 kDa fragment during thymic apoptosis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026443926962
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  • 65
    Digitale Medien
    Digitale Medien
    Activation of a CPP32-like protease during L1210 cell apoptosis induced by thiol deprivation (1997)
    Springer
    Apoptosis 2 (1997), S. 77-83 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; bcl-2 ; CPP32 ; thiol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Reduced thiols (e.g., cysteine) are important in the maintenance of lymphocyte cell viability and growth. L1210 monocytic leukaemia cells were known to have a limited ability to uptake cystine, and they require cysteine for cell growth. L1210 cells underwent apoptosis when cultured without thiol-bearing and dithiol-cleaving compounds, adding thiols suppressed the apoptosis and promoted cell growth. A specific inhibitor of interleukin-1 β-converting enzyme (ICE)-like and CPP32-like proteases could suppress L1210 cell apoptosis induced by thiol deprivation. The cell lysates of apoptotic L1210 cells exhibited protease activity that could cleave DEVD-AMC, but not YVAD-AMC, and so CPP32-like proteases, but not ICE-like proteases, were activated and participated in apoptosis. The addition of thiols could suppress CPP32-like protease activation. Although the cell death-suppressor bcl-2-family proteins (bcl-2 and bcl-XL) were recently found to suppress the activation of CPP32-like proteases, the expression levels of death-suppressor bcl-2-family proteins did not change when thiols were added. These results suggest that reduced thiols maintain L1210 cell survival by inhibiting the activation of CPP32-like proteases without changing the anti-apoptotic bcl-2-family protein expression.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026491810123
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  • 66
    Digitale Medien
    Digitale Medien
    Cytokeratin-19 associated with apoptosis and chemosensitivity in human cervical cancer cells (1997)
    Springer
    Apoptosis 2 (1997), S. 101-105 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; cytokeratin ; drug resistance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Cytokeratins are one group of intermediate filament proteins responsible for the integrity of cell structure, and have been recently reported to play a role in conferring a drug resistance phenotype. MAb Cx-99 is a monoclonal antibody exhibiting the specificity toward its corresponding antigen which was recently identified as the cytokeratin-19 protein. In the present study, we found that the level of cytokeratin-19 in cervical cancer cells could be decreased by incubation of cancer cells with MAb Cx-99. The reduction of cytokeratin-19 level had a killing effect on cervical carcinoma SIHA and HeLa S3 cell lines. The DNA ladder pattern, convoluted nuclei and blebbing morphology were observed with these cells after exposure to MAb Cx-99 for 72 h, suggesting that the cytotoxic mechanism of reduced cytokeratin-19 was mediated by induction of apoptosis. Moreover, the MAb Cx-99 treatment could increase the cytotoxicities of cancer chemotherapeutic agents such as cisplatin and vinblastine to both cervical carcinoma cell lines. The LD80 values were at least 15-fold reduced when cancer cells were treated with cisplatin or vinblastine in the presence of MAb Cx-99. These results suggest that the functional role of cytokeratin-19 was associated with the apoptosis prevention and drug resistance of cervical cancer cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026448027870
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  • 67
    Digitale Medien
    Digitale Medien
    Evidence for an interleukin-1β converting enzyme (ICE)-like activity distinct from ICE and responsible for ICE and CPP32 cleavage during apoptosis (1997)
    Springer
    Apoptosis 2 (1997), S. 125-135 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; CPP32 ; ICE ; ICE inhibitors ; ICE-related protease
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract IL-1β converting enzyme (ICE) and ICE-related proteases (IRPs) have been suggested to play a central role in apoptosis. We report the use of peptidic ICE inhibitors to reassess the role of this enzyme in the apoptosis induced by Fas or TNFα receptor ligation in Jurkat cells, U937 cells or monocytes. Our results show that inhibition of IL-1β processing can be dissociated from inhibition of apoptosis. Indeed, two out of three com-pounds active on ICE are not inhibitory for apoptosis. This shows that ICE is not required for progression in the apoptotic pathway, but that one or several IRPs are necessary. In addition, Western blot analysis of cell lysates shows that both ICE and CPP32 precursors disappear rapidly after apoptosis induction, while ICH-1L precursor remains intact. Concomitant appearance of cleavage products can be visualized for CPP32, but not for ICE, suggesting that the former is proteolytically activated. In addition, this precursor cleavage can be blocked by an ICE inhibitor active on apoptosis. Altogether, our data support the hypothesis that one or several IRPs are necessary for apoptosis and are responsible for ICE and CPP32 cleavage during this process.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026404212849
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  • 68
    Digitale Medien
    Digitale Medien
    The proto-oncogene Bcl-2 inhibits cellular toxicity of dopamine: possible implications for Parkinson's Disease (1997)
    Springer
    Apoptosis 2 (1997), S. 149-155 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; bcl-2 ; dopamine ; Parkinson's disease ; PC-12 ; proto-oncogene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract It is currently believed that excessive oxidant stress induced by metabolism of dopamine (DA), plays a major role in the pathogenesis of the selective nigrostriatal neuronal loss in Parkinson's disease. We recently showed that the neurotransmitter DA, in physiological concentrations, is capable of initiating apoptosis in cultured, post-mitotic sympathetic neurons. Bcl-2 is a proto-oncogene that blocks apoptosis. We now report that Bcl-2 is a powerful inhibitor of DA toxicity in PC-12 pheochromocytoma cells. We induced stable expression of Bcl-2 in PC-12 cells by transfection with recombinant pCMV5 expression vector, containing mouse bcl-2 (coding-sequence) cDNA. Cells expressing Bcl-2 manifested marked resistance to otherwise lethal (300 uM) in vitroconcentrations of DA. This protective effect was reflected in the trypan-blue test of cell survival, 3 H-thymidine incorporation and inhibition of the characteristic apoptotic morphologic alterations in scanning electron microscopic studies. Bcl-2 and associated control systems of apoptosis may have an important physiological role in restraining the apop-tosis-triggering potential of DA in nigrostriatal neurons. This novel field of research may yield insights into the pathogenesis of Parkinson's disease and lead to development of novel therapeutic approaches.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026408313758
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  • 69
    Digitale Medien
    Digitale Medien
    Superoxide, nitric oxide, peroxynitrite and cytokine combinations all cause functional impairment and morphological changes in rat islets of Langerhans and insulin secreting cell lines, but dictate cell death by different mechanisms (1997)
    Springer
    Apoptosis 2 (1997), S. 164-177 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; beta cells ; cytokines ; Islets of Langerhans ; nitric oxide ; peroxynitrite ; superoxide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract We have shown that nitric oxide treatment for 30–90 min causes inhibition of insulin secretion, DNA damage and disturbs sub-cellular organization in rat and human islets of Langerhans and HIT-T15 cells. Here rat islets and beta-cell lines were treated with various free radical generating systems S-nitrosoglutathione (nitric oxide), xanthine oxidase plus hypoxanthine (reactive oxygen species), 3-morpholinosydnonimine (nitric oxide, super-oxide, peroxynitrite, hydrogen peroxide) and peroxynitrite and their effects over 4 h to 3 days compared with those of the cytokine combination interleukin-1β, tumour necrosis factor-α and interferon-γ. End points examined were de novo protein synthesis, cellular reducing capacity, morphological changes and apoptosis by acridine orange cytochemistry, DNA gel electrophoresis and electron microscopy. Treatment (24–72 h) with nitric oxide, superoxide, peroxynitrite or combined cytokines differentially decreased redox function and inhibited protein synthesis in rat islets of Langerhans and in insulin-containing cell lines; cytokine effects were arginine and nitric oxide dependent. Peroxynitrite gave rare apoptosis in HIT-T15 cells and superoxide gave none in any cell type, but caused the most beta cell-specific damage in islets. S-nitroso-glutathione was the most effective agent at causing DNA laddering or chromatin margination characteristic of apoptotic cell death in insulin-containing cells. Cytokine-induced apoptosis was observed specifically in islet beta cells, combined cytokine effects on islet function and death most resembled those of the mixed radical donor SIN-1.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026412414666
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  • 70
    Digitale Medien
    Digitale Medien
    Spontaneous death of isolated adult rat cardiocytes in culture in association with internucleosomal cleavage of genomic DNA (1997)
    Springer
    Apoptosis 2 (1997), S. 178-188 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; enzyme immunoassay ; gel electrophoresis ; growth factor ; immunohistochemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Many isolated adult cardiocytes do not survive beyond the early days of culture, but why they die has not been defined. We examined the possibility of apoptosis as the mechanism of death in cultured atrial and ventricular rat cardiocytes. Calcium-tolerant cardiocytes isolated by enzymatic dissociation were cultured with a medium containing FBS. Nucleosomal DNA fragmentation was detected by electrophoresis of DNA extracted from the cardiocytes, by immunohistochemical in situ DNA nick-end labelling of single cells, and by enzyme immunoassay for in vitro quantification in cytoplasmic fraction. Electrophoresis on the 5th to 14th day of culture revealed the ladder appearance characteristic of internucleosomal DNA cleavage in apoptosis with a consistent single peak of increased cytoplasmic DNA fragments. After the 14th day, the cytoplasmic DNA fragments decreased, and the ladder appearance could no longer be detected by electrophoresis. Cardiocytes positive with nick-end labelling were seen by the 5th day, and then increased in number over the remaining days. These results indicate that many isolated cardiocytes die spontaneously by apoptosis within the first 2 weeks of culture, suggesting a possible signal dependence for survival of adult cardiocytes. In addition to chemical signal depletion in culture, other possible explanations for this apoptosis include the absence of an electric signal during culture, lack of contractile activity, and initial loss of intercellular connections.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026464431505
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  • 71
    Digitale Medien
    Digitale Medien
    Radiation-induced apoptosis and its relationship to loss of clonogenic survival (1997)
    Springer
    Apoptosis 2 (1997), S. 265-282 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; cell cycle ; clonogenicity ; p53 ; radiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Ionizing radiation can be an effective inducer of apoptosis and studies of many aspects of the pathways and mechanisms involved in this apoptosis induction have been published. This review stresses two aspects: the relationship between apoptosis and loss of clonogenic ability in irradiated cells and the time course for the appearance of apoptosis after radiation exposure. Although it was initially assumed that apoptosis occurred relatively quickly (within hours) after irradiation, evidence is presented and discussed here showing that apoptosis can occur at long times after irradiation (out to 20 days) in some cell types. This late, or delayed, apoptosis occurs after the cells have divided once or several times. The impact of delayed apoptosis on loss of clonogenicity after irradiation remains unclear. It seems likely that in some cell types, e.g., fibroblasts, the occurrence of late apoptosis is minimal and may have little impact on long term cell survival of the population, but in at least one instance, with a cell line of hematopoietic origin, it appears that late apoptosis can account for all the loss of clonogenicity in irradiated cells. The role of p53 in radiation-induced apoptosis is also discussed, with data presented showing that both p53-dependent and independent pathways for radiation-induced apoptosis exist, depending on the cell type.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026485003280
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  • 72
    Digitale Medien
    Digitale Medien
    Butyrate-induced reversal of dexamethasone resistance in autonomous rat Nb2 lymphoma cells (1997)
    Springer
    Apoptosis 2 (1997), S. 518-528 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; Bcl-2 ; dexamethasone ; Nb2 lymphoma ; Pim-1 ; prolactin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The parental rat Nb2 lymphoma is a prolactin (PRL)-dependent T cell line. Exposure of a PRL-independent subline, Nb2-SFJCD1, to sodium butyrate (NaBT) causes transient reversal of their growth factor-independent proliferation in association with constitutive expression of protooncogenes pim-1and c-myc. In the present study, we investigated the effect of NaBT treatment on the sensitivity of Nb2-SFJCD1 cells to dexamethasone (DEX)-induced apoptosis. Pretreatment with NaBT (2 mM, 72 h) partially reversed resistance to apoptosis in Nb2-SFJCD1 cells exposed to DEX (100 nM) for 12 h, assessed by flow cytometric analyses of DNA fragmentation. However, the cytolytic effect of DEX was abrogated by PRL i n a time- and concentration-dependent manner. Eval uati on of apoptosis-associated gene expression in NaBT-pre-treated cultures incubated with DEX or DEX+PRL indicated that the apoptosis resistance did not stem from altered bcl-2 or bax expression. However, there was a strong correlation between the resistance to DEX-activated apoptosis and their enhanced expression of pim-1 mRNA and protein. The results show that it is possible to reverse DEX-induced apoptosis of Nb2 pre-T cells and suggest the pim-1 gene product has an important role as a suppressor of this process, perhaps functioning as a mediator of PRL action.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026438615092
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  • 73
    Digitale Medien
    Digitale Medien
    Accumulation of major stress protein 70kDa protects myeloid and lymphoid cells from death by apoptosis (1997)
    Springer
    Apoptosis 2 (1997), S. 156-163 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; hsp70 ; liposomes ; quercetin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The major heat shock protein, hsp70, is known to contribute to the mechanisms of cell protection against a variety of stress and cytotoxic factors, providing an increase of cell survival. Whether hsp70 could be implicated in the rescue of cells from stress-induced death proceeding on apoptotic pathway is not well established. Here we report that susceptibility of myeloid and lymphoid cell lines to apoptosis induced by heat shock or ethanol coincides with hsp70 content and can be modulated by changes in expression of this protein. Cells of lymphoid and myeloid lines differing in basal and inducible level of the protein were tested. The cells containing higher amounts of hsp70 (U937, Jurkat, Molt4) were more resistant to the apoptosis-inducing stimuli then cells which accumu-late lower amounts of the protein (HL60) and especially those lacking the protein (NSO). Inhibition of hsp70 accumulation by quercetin made cells more susceptible to the same apoptotic inducer. Enhancement of hsp70 expression by previous heating or by liposomal delivery of the exogenic protein to the cells lacking hsp70 made them more resistant to apoptosis. The possible mechanisms of the hsp70 protective effect in apoptosis are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026460330596
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  • 74
    Digitale Medien
    Digitale Medien
    Human keratinocytes maintain reversible anti-apoptotic defenses in vivo and in vitro (1997)
    Springer
    Apoptosis 2 (1997), S. 136-148 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; bcl-2 ; keratinocytes ; proto-oncogene ; ultraviolet radiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Human keratinocytes proliferate and differentiate in an epidermal environment where induction of apoptosis can be triggered by ultraviolet radiation (UVR), activated lymphocytes and cytokines. The purpose of this study was to determine whether keratinocytes were susceptible to apoptosis induced by ionophore, ultra-violet radiation, cytokines or crosslinking of CD95 (Fas/APO-1). In normal human skin exposed to two minimal erythema doses of ultraviolet radiation, suprabasal cells were the first keratinocytes to demonstrate apoptotic nuclei, and by 48 h apoptotic cells were identified throughout the mid to upper epidermis. However, most keratinocytes resisted apoptosis and UVR-induced apoptosis was not observed in basal cells, or in the most differentiated epidermis. Human keratinocytes and keratinocyte cell lines cultured in vitro developed maximal apoptosis 48 h after radiation. Human keratinocytes cultured in full growth factor supplements were resistant to UVR-induced apoptosis compared to keratinocyte cell lines or to a lymphoid cell line (HL60) susceptible to apoptosis. Keratinocyte cell lines were completely resistant to apoptosis induced by interferon-γ, interferon-α, IL-2, IL-6, TNF-α, IL-1Ra, and GM-CSF. A subset of the cells in cultures of keratinocytes and transformed keratinocyte cell lines died by apoptosis in response to anti-Fas, IL-1α and TNF-α plus IFN-γ and ionophore. Second passage freshly isolated human keratinocytes were much more resistant to apoptosis induced by ionophore, anti-Fas and cytokines than were transformed keratinocyte cell lines. Calcium shift to induce differentiation in second-passage keratinocyte cultures made keratino-cytes even more resistant to UVR-induced apoptosis. This parallels the lack of UVR-induced apoptosis observed in the most differentiated keratinocytes in irradiated human skin. Both keratinocytes and kerati-nocyte cell lines express rather low levels of the anti-apoptotic proteins bcl-2 and bcl-x compared to other apoptosis-resistant cell types. The differences between keratinocytes and keratinocyte cell lines in suscepti-bility to apoptosis are not explained by difference in expression of bcl-2 or bcl-x. Finally, withdrawal of growth factors from keratinocytes decreased cell survival following UVR and increased the induction of apoptosis. Inhibition of protein synthesis with cyclo-heximide also made keratinocytes more susceptible to UVR-induced apoptosis, indicating that anti-apop-totic defences in cultured keratinocytes are dependent on active protein synthesis. These experiments show that the strong keratinocyte defences against apoptosis are stratified within the epidermis, and can be altered by differentiation and growth factor withdrawal.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026456229688
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  • 75
    Digitale Medien
    Digitale Medien
    Cell cycle G2/M arrest and activation of cyclin-dependent kinases associated with low-dose paclitaxel-induced sub-G1 apoptosis (1997)
    Springer
    Apoptosis 2 (1997), S. 463-470 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; CDC 2 (CDK 1) ; CDK 7 ; cyclin B1 ; G2/M arrest ; paclitaxel (Taxol(tm))
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Paclitaxel is a potential anti-cancer agent for several malignancies including ovary, breast, and head and neck cancers. This study investigated the kinetics of paclitaxel-induced cell cycle perturbation in two human nasopharyngeal carcinoma (NPC) cell lines, NPC-TW01 and NPC-TW04. NPC cells treated with higher concentrations (0.1 or 1 µM) of paclitaxel showed obvious G2/M arrest and then converted to a cell population with reduced DNA content, which was detected as a sub-G2 peak in the flow cytometric histographs. If a low concentration (5 nM) of paclitaxel was used instead, transient G2/M arrest was observed in NPC cells, which subsequently converted to a sub-G1 form during the treatment period. Internucleosomal fragmentation and chromatin condensation were detectable in these sub-G1 and sub-G2 cells, suggesting that persistent or transient G2/M arrest is a prerequisite step for apoptosis elicited by varying doses of paclitaxel. The levels of cyclins A, B1, D1, E, CDK 1 (CDC 2), CDK 2 and proliferating cell nuclear antigen (PCNA) were unchanged in NPC cells following treatment with any concentration of paclitaxel; however, apoptosis-related cyclin B1-associated CDC 2 kinase was highly activated by paclitaxel even at concentrations as low as 5 nM, which is consistent with the finding that low-dose paclitaxel is also able to induce apoptosis in NPC cells. Activation of cyclin B1-associated CDC 2 kinase seems to be an important G2/M event required for paclitaxel-induced apoptosis, and this activation of cyclin B1/CDC 2 kinase could be attributed to the increased activity of CDK 7 kinase.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026422111457
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  • 76
    Digitale Medien
    Digitale Medien
    Intraepithelial lymphocytes vs. colorectal neoplastic cells: Who is winning the apoptotic battle? (1997)
    Springer
    Apoptosis 2 (1997), S. 489-493 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; intraepithelial lymphocytes ; colorectal adenomas
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Intraepithelial lymphocytes (IELs) and Intraepithelial apoptotic granules (AGs) are found in the vast majority of colorectal adenomas, less frequently in incipient carcinomas and occasionally in advanced colorectal carcinomas. In colorectal adenomas, the activated and cytotoxic IELs undergo apoptosis by a Fas-FasL mechanism. In advanced invasive carcinomas lacking IELs, that mechanism cannot be activated. On the other hand, the peritumoural lymphocytes which surround some advanced invasive carcinomas may abrogate to-be-metastatic tumor cells, as treated cancer patients with peritumoural lymphocytes have a better 5-years' survival than those without that peritumoural barrier. In colorectal adenomas the host reaction (IELs) dysplastic cells Fas-dependent confrontation seems to prevent rapidly proliferating adenomas from becoming rapidly invasive carcinomas, since that process takes 10 to 20 years to evolve.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026430313275
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  • 77
    Digitale Medien
    Digitale Medien
    Intracellular alkalinization in dexamethasone-induced thymocyte apoptosis (1997)
    Springer
    Apoptosis 2 (1997), S. 304-312 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; intracellular pH ; ion transporter ; thymocytes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Glucocorticoid can induce apoptosis of thymocytes, but its mechanism is not clear yet. In this study, we reported that dexamethasone-induced apoptosis was associated with intracellular alkalinization. Dexamethasone induced a higher percentage of apoptosis in 138 mM than in 50 mM NaCl, total abrogation of apoptosis was noted in NaCl-depleted culture medium. Highest apoptotic rate was observed in medium with pH 7.2, whereas it was partially and completely inhibited at pH 6.5 and pH 6.0, respectively. Intracellular pH was higher in pre-apoptotic thymocytes than non-apoptotic ones. The Na+ /H+ antiporter inhibitor of 5-(N,N'-dimethyl)-amiloride inhibited the dexamethasone-induced increase in pHi and apoptosis of thymocytes. Glucocorticoid antagonist RU486 also blocked the dexamethasone-induced effect. Furthermore, the apoptosis and increase in intracellular pH induced by dexamethasone were inhibited by cycloheximide, actinomycin D. It seems that intracellular pH is increased during the development of thymocyte apoptosis and inhibiting its increment would retard the rate of progression to cell death.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026441221027
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  • 78
    Digitale Medien
    Digitale Medien
    The treatment with differentiation- and apoptosis-inducing agent, vesnarinone, of a patient with oral squamous cell carcinoma (1997)
    Springer
    Apoptosis 2 (1997), S. 313-318 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; differentiation ; oral squamous cell carcinoma ; vesnarinone
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract A patient with histopathological recurrent oral cancer with well-differentiated squamous cell carcinoma, was treated with differentiation- and apoptosis-inducing agent, vesnarinone, per os at a dose of 180 mg/day for 56 days and then at a dose of 60 mg/day for 93 days. The vesnarinone administration caused complete remission of the tumour. It has been found by immunohistochemical staining and PCR-SSCP analysis that the recurrent tumour has wild type p53 gene and relative high level of LeY expression as well as DNA fragmentation in the cancer cells, as assessed by nick-end labelling. These findings suggest that the cure of oral squamous cell carcinoma observed in this case might be associated with induction of differentiation and apoptosis of cancer cells by vesnarinone.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026493205097
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  • 79
    Digitale Medien
    Digitale Medien
    Regulation of apoptosis-associated proteins in cell death following transient focal ischemia in rat pups (1997)
    Springer
    Apoptosis 2 (1997), S. 368-376 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; Bax ; Bcl2 ; cerebral neonatal ischemia ; hsp72 ; immunohistochemistry ; p53
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Apoptosis is a process whereby developmental or environmental stimuli activate a genetic programme to execute a specific series of events that culminate in the death and efficient disposal of a cell. Although a series of recent data suggested that neuronal death following cerebral ischemia occurs through an apoptotic pathway, additional work is needed to establish the existence of a causal relationship between gene expression and DNA breaks in neuronal death. We investigate the role of p53 and Bax proteins in the induction of apoptosis induced by a new transient focal ischemia model in the rat pup. Our results show that wild-type p53 exerts a significant and time-dependent effect in the initiation of apoptosis, and that apoptosis is induced via DNA-strand breakage. Subsequently, increased Bax expression was observed in the cytoplasm of dying cells located in the infarct, whereas an increased Bcl-2 and hsp72 staining was detectable in survival cells and reactive glia present at the periphery of the lesion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026453623753
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  • 80
    Digitale Medien
    Digitale Medien
    BAG-1 inhibits p53-induced but not apoptin-induced apoptosis (1997)
    Springer
    Apoptosis 2 (1997), S. 395-402 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; apoptin ; BAG-1 ; Bcl-2 ; p53 ; programmed cell death
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract BAG-1 has been identified as a Bcl-2-binding protein that inhibits apoptosis, either alone or in co-operation with Bcl-2. Here we show that BAG-1 inhibits p53- induced apoptosis in the human tumour cell line Saos-2. In contrast, BAG-1 was unable to inhibit the p53-independent pathway induced by apoptin, an apoptosis-inducing protein derived from chicken anaemia virus. Whereas BAG-1 seemed to co-operate with Bcl-2 to repress p53-induced apoptosis, co-expression of these proteins had no inhibitory effect on apoptin-induced apoptosis. Moreover, Bcl-2, and to some extent also BAG-1, paradoxically enhanced the apoptotic activity of apoptin. These results demonstrate that p53 and apoptin induce apoptosis through independent pathways, which are differentially regulated by BAG-1 and Bcl-2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026409808732
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  • 81
    Digitale Medien
    Digitale Medien
    Apoptotic myocardial degeneration in thrombotic thrombocytopenic purpura (1997)
    Springer
    Apoptosis 2 (1997), S. 384-394 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; cardiac conduction system ; cardiogenic hypertensive chemoreflex ; myocardial ischemia ; platelets ; thrombotic thrombocytopenic purpura
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The objective of this study was to determine whether the known myocardial degeneration in TTP is due to apoptosis. In TTP the heart is often involved, including the cardiac conduction system. Despite many platelet occlusions of small coronary arteries, there is little myocardial necrosis. Why the intermittent clinical episodes begin or end is unknown. Six hearts of patients dying with TTP were examined with routine and immunohistochemical stains. In addition to ventricular and atrial myocardium we examined the cardiac conduction system and coronary chemoreceptor. Numerous small coronary arteries were occluded with platelet thrombi in all these sites, including especially the sinus node, AV node and His bundle. The myocardial degeneration we found was conspicuously devoid of inflammation and the myocytes were relatively intact. These characteristics combined with TUNEL-positivity in the degenerating cells are typical of apoptosis. The focal degeneration in TTP is primarily apoptotic. Because circulating serotonin is carried by platelets and is released during aggregation, and because serotonin can cause a powerful cardiogenic hypertensive chemoreflex, we suggest that such a response may dislodge early platelet aggregations. Lessons from TTP may have special relevance for better understanding of myocardial reperfusion problems associated with angioplasty, thrombolysis and ischemic preconditioning.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026457724661
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  • 82
    Digitale Medien
    Digitale Medien
    Oestradiol inhibits spontaneous and cisplatin-induced apoptosis in epithelial ovarian cancer cells: relationship to DNA repair capacity (1997)
    Springer
    Apoptosis 2 (1997), S. 478-484 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; cisplatin ; DNA repair ; epithelial ovarian cancer cells ; oestradiol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract A prospective role of sex steroid hormones in the pathogenesis of common epithelial ovarian cancer remains equivocal. We hypothesized that oestradiol can protect ovarian cells from apoptosis by augmenting their DNA repair capacity. Two established oestrogen receptor-positive human cancer cell lines of ovarian surface epithelial origin (OVCAR-3, SKOV-3) were studied during short-term (24 h) subculture in the absence or presence of oestradiol-17β and/or the DNA-damaging chemotherapeutic agent cisplatin. Apoptosis was monitored among individual cells by in situ DNA fragmentation analysis. Basal rates of apoptosis were diminished by exposure to oestradiol (progesterone or testosterone were without effect). Oestradiol also suppressed apoptosis induced by cisplatin and enhanced the repair of a cisplatin-damaged reporter chloramphenicol-O-acetyltransferase gene transfected into ovarian cells. The ability of oestrogen-responsive ovarian cancer cells to efficiently repair DNA and thereby avoid apoptosis may be related to propensity for clonal expansion and drug resistance.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026426212366
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  • 83
    Digitale Medien
    Digitale Medien
    Role of XIAP protein, a human member of the inhibitor of apoptosis (IAP) protein family, in phytohemagglutinin-induced apoptosis of human T cell lines (1997)
    Springer
    Apoptosis 2 (1997), S. 501-509 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; human T cells ; signal transduction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract A new family of human genes xiap, hiap-1 and hiap-2, which are homologous to the baculovirus iap (inhibitor of apoptosis) genes cp-iap and op-iap, has been recently cloned and shown to suppress apoptosis after serum withdrawal or exposure to a free radical inducer. In order to examine the role of one of these human genes, namely xiap, in lymphoid cells, we studied XIAP expression, after PHA stimulation in three different human T cell lines. We report here that stimulation with PHA resulted in the human T cell lines undergoing apoptosis, as assessed by DNA fragmentation and by propidiumiodide (PI) staining and flow cytometry. When XIAP protein expression was evaluated by Western blot, we observed that the induction of apoptosis by PHA was associated with a parallel decrease of XIAP expression. We also provide evidence that stably transfected Jurkat cells containing the xiap open reading frame became resistant to PHA-induced apoptosis. These data suggest a role for XIAP protein in the regulation of apoptosis in lymphoid cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026434514183
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  • 84
    Digitale Medien
    Digitale Medien
    Inhibition of protein synthesis sensitizes thermotolerant cells to heat shock induced apoptosis (1997)
    Springer
    Apoptosis 2 (1997), S. 510-517 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; comet assay ; hyperthermia ; thermotolerance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Hyperthermia is a potent inducer of apoptosis in many cell lines. A brief exposure to mildly elevated temperatures elicits a transient state of augmented resistance to subsequent thermal stress. Here we show that a hyperthermic treatment of 43°C for 1 h is sufficient to induce apoptosis in the cell line HL-60. This observation is based on morphologic evaluation and on comet assay results (an extremely sensitive method of detecting and quantifying apoptotic DNA fragmentation in individual cells). The thermotolerance phenomenon was also verified in the same manner by giving the cells a brief 30 min sub-lethal heat conditioning treatment at 43°C followed by a 6 h incubation time prior to the administration of a lethal heat load (43°C for 1 h). We observed a dramatic decrease in resultant apoptoses in the thermotolerized cells in comparison to unconditioned cells. We assessed the necessity of de novo protein synthesis in the protective phenomenon. When the conditioned cells were given a cycloheximide treatment prior to heat conditioning we saw a sensitization of the conditioned cells to secondary thermal injury.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026486531021
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  • 85
    Digitale Medien
    Digitale Medien
    An Uncoupling of the Processes of Oxidation and Phosphorylation in Glycolysis (1997)
    Springer
    Bioscience reports 17 (1997), S. 521-527 
    Details
    ISSN: 1573-4935
    Schlagwort(e): Glyceraldehyde-3-phosphate dehydrogenase ; glycolysis ; oxidation ; uncoupling ; thiols ; hydrogen peroxide ; mitochondria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Data on alterations of the properties of glyceraldehyde-3-phosphate dehydrogenase upon oxidation of its functional groups are reviewed; a mechanism of uncoupling of oxidation and phosphorylation in glycolysis is considered. Possible ways of regulating uncoupling, and the physiological importance of this process, are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1027356106330
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  • 86
    Digitale Medien
    Digitale Medien
    Apoptosis Dependent Decrease of the Intramembrane Ion Traffic in Cultured Mouse Fibroblasts Shown by Conductivity Dispersion (1997)
    Springer
    Bioscience reports 17 (1997), S. 547-556 
    Details
    ISSN: 1573-4935
    Schlagwort(e): Apoptosis ; conductivity ; dielectric ; fibroblast
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract We have investigated the intramembranal ion traffic in apoptotic 3T6 cells in culture. Apoptosis was induced by various treatments, such as serum deprivation, high density growth and hydrogen peroxide at subnecrotic doses. Cell death was assessed by nucleosomal DNA fragmentation, single cell electrophoresis, immunofluorescence and histological staining. To study the modifications of membrane structure and function, we adopted a well established biophysical strategy based on the measurement of the electrical conductivity of cell suspensions, as a function of the frequency of the electrical field applied to the sample. A comparison between the conductivity of normal and apoptotic cell suspensions shows that programmed cell death causes a decrease of membrane conductivity which indicates a diminished intramembranal ion traffic. Our results strongly suggest that one of the early events in the triggering of apoptosis is represented by an overall reduction of plasma membrane function. Finally, our results are in agreement with the idea that the nucleus is not the sole target of the apoptotic process.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1027364308147
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  • 87
    Digitale Medien
    Digitale Medien
    Geochemistry and acidity of sulphide-bearing postglacial sediments of western Finland (1997)
    Springer
    Environmental geochemistry and health 19 (1997), S. 155-164 
    Details
    ISSN: 1573-2983
    Schlagwort(e): geochemistry ; metals ; sulphide sediment ; oxidation ; acidification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Medizin
    Notizen: Abstract The geochemistry, mineralogy, acidity and electric conductivity of sulphide-bearing postglacial sediments located on the coastal plains of western Finland were studied. Grain size and mineralogical analysis (eight samples studied) indicated that the sediments are silts dominated by primary minerals (quartz, feldspars), and that the clay fraction (〈2µm), which made up less than one-third of the bulk samples, is enriched in phyllosilicates but depleted in quartz and feldspars, relative to bulk samples. As compared to the metal contents of the fine-fraction of glacial till (data of the Geological Survey of Finland), the fine sediments appear to be enriched in sulphur (median = 0.54%) and trace metals such as Ni (31 µg g−1), Zn (90 µg g−1), Co (13 µg g−1), Cr (48 µg g−1) and V (50 µg g−1). Statistical analysis indicated that aluminosilicates are the principal carrier phases of trace metals, and that sulphides and organic matter only partially control the distribution of elements other than S and C. A 3-g portion of 232 samples was oxidised in the laboratory by atmospheric oxygen for a period of 1 year. After this period of oxidation, 15 ml of water was added, after which pH and electric conductivity of the suspensions (sediment:water, 1:5) were measured. The quantities of elements mobilised by the oxidation was calculated from the dissolved concentrations found in 3 g of oxidised sediment suspended in 30 ml of deionised water (eight samples studied). The results of the experiment showed that the impact of sulphide oxidation on the pH and conductivity of the sediments is large, and that a high proportion (〉13%) of the aqua-regia extractable contents of several elements (Co, Mn, Ca, Ni, Zn, Sr, Na and B) are mobilised at oxidation. Because of the high quantities of acidity and metals liberated at oxidation, it is argued that stream-water quality, which is poor in the study area, will not improve unless artificial draining is restricted in areas of sulphide sediments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1018462824486
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  • 88
    Digitale Medien
    Digitale Medien
    Gas-phase catalytic oxidation ofm-xylene (1997)
    Springer
    Reaction kinetics and catalysis letters 62 (1997), S. 117-120 
    Details
    ISSN: 1588-2837
    Schlagwort(e): m-xylene ; oxidation ; gas-phase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The gas-phase oxidation ofm-xylene on catalysts for partial hydrocarbon oxidation (Bi−Fe−Co−Ni−Mo−P−O, V−Sb−O and V−Ti−O) has been studied at 325–400°C. 3-Methylbenzaldehyde (for the first two catalysts), or both 3-methylbenzaldehyde and 3-methylbenzoic acid (for the last one) were shown to be the main partial oxidation products.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02475721
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  • 89
    Digitale Medien
    Digitale Medien
    Kinetic study of methane oxidation over perovskite oxides La1−xSrxCoO3 (1997)
    Springer
    Reaction kinetics and catalysis letters 62 (1997), S. 185-190 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Methane ; oxidation ; La1−xSrxCoO3
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Methane oxidation over perovskite oxide (La1−xSrxCoO3) were investigated under rich oxygen circumstance. The large x in oxide or the higher temperature will promote the lattice oxygen to participate in the reaction. The relative adsorption properties of catalyst and reaction kinetic were also studied.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02475731
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  • 90
    Digitale Medien
    Digitale Medien
    Effect of structural disorder on the catalytic activity of mixed La−Sr−Co−Fr−O perovskites (1997)
    Springer
    Reaction kinetics and catalysis letters 62 (1997), S. 129-135 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Perovskite ; defect structure ; carbon monoxide ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract For a perovskite system La0.7Sr0.3Co1-xFexO3, the effect of partial substitution of Co by Fe on the particle microstructure and chemical composition of the surface layer has been studied. Iron incorporation was found to cause a structure rearrangement from the hexagonal (at x〈0.05) to the cubic (atx〉0.05) type, which was not accompanied by any appreciable variation of the surface layer composition. A transient sample with x=0.05 was characterized by a high degree of misorientation of microblocks and had the highest activity in the CO catalytic oxidation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02475723
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  • 91
    Digitale Medien
    Digitale Medien
    Zirconium(IV) catalysis in perborate oxidation of iodide (1997)
    Springer
    Reaction kinetics and catalysis letters 60 (1997), S. 387-394 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Perborate ; iodide ; zirconium(IV) ; catalysis ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Zirconium(IV) catalyzes perborate oxidation of iodide ion. In acidic solution the oxidation is zero order with respect to perborate, first order with respect to Zr(IV), independent of [H+] and exhibits Michaelis-Menten dependence on [I−]. Mechanistic pathway of the catalysis is discussed and a rate equation is derived.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02475703
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  • 92
    Digitale Medien
    Digitale Medien
    Induction of apoptosis by protein kinase C pseudosubstrate lipopeptides in several human cells (1997)
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 397-402 
    Details
    ISSN: 1573-3904
    Schlagwort(e): Apoptosis ; Protein kinase C ; Pseudosubstrate sequence ; Lipopeptide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Intracellular enzymes or receptors are interesting targets for thepharmacomodulation of cellular metabolism. We have previously shown thatmodification of relatively long peptides by a palmitoyl-lysine residue couldfacilitate their delivery into the cytoplasm of living cells. Severalpeptides containing pseudosubstrate sequences of protein kinase C (PKC) havebeen evaluated for their ability to modulate phosphorylation of modelsubstrate, neuronal morphology or tumor necrosis factor secretion. In thiswork we have evaluated the effect of palmitoyl-modified PKC-pseudosubstratepeptides on induction of apoptosis. We have established that these peptidesare able to induce apoptosis in different human cell types (primaryfibroblasts, T- and B-lymphocyte cell lines) as assessed by (terminal deoxynucleotidyl transferase dUTP nick-end labelling) and DNAfragmentation. In contrast, control peptides (non-lipidicPKC-pseudosubstrate peptides and irrelevant lipopeptides) had no or littleeffect on programmed cell death. This work highlights the pharmacologicalinterest of lipopeptides and argues in favor of the potential role of PKC(s)in the cell death machinery.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008833929317
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  • 93
    Digitale Medien
    Digitale Medien
    Induction of apoptosis by protein kinase C pseudosubstrate lipopeptides in several human cells (1997)
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 397-402 
    Details
    ISSN: 1573-3904
    Schlagwort(e): Apoptosis ; Protein kinase C ; Pseudosubstrate sequence ; Lipopeptide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Intracellular enzymes or receptors are interesting targets for the pharmacomodulation of cellular metabolism. We have previously shown that modification of relatively long peptides by a palmitoyl-lysine residue could facilitate their delivery into the cytoplasm of living cells. Several peptides containing pseudosubstrate sequences of protein kinase C (PKC) have been evaluated for their ability to modulate phosphorylation of model substrate, neuronal morphology or tumor necrosis factor secretion. In this work we have evaluated the effect of palmitoyl-modified PKC-pseudosubstrate peptides on induction of apoptosis. We have established that these peptides are able to induce apoptosis in different human cell types (primary fibroblasts, T- and B-lymphocyte cell lines) as assessed by (terminal deoxynucleotidyl transferase dUTP nick-end labelling) and DNA fragmentation. In contrast, control peptides (non-lipidic PKC-pseudosubstrate peptides and irrelevant lipopeptides) had no or little effect on programmed cell death. This work highlights the pharmacological interest of lipopeptides and argues in favor of the potential role of PKC(s) in the cell death machinery.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02442906
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