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  • 1
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Collagens of most connective tissues are subject to continuous remodelling and turnover, a phenomenon which occurs under both physiological and pathological conditions. Degradation of these proteins involves participation of a variety of proteolytic enzymes including members of the following proteinase classes: matrix metalloproteinases (e.g. collagenase, gelatinase and stromelysin), cysteine proteinases (e.g. cathepsin B and L) and serine proteinases (e.g. plasmin and plasminogen activator). Convincing evidence is available indicating a pivotal role for matrix metalloproteinases, in particular collagenase, in the degradation of collagen under conditions of rapid remodelling, e.g. inflammation and involution of the uterus. Under steady state conditions, such as during turnover of soft connective tissues, involvement of collagenase has yet to be demonstrated. Under these circumstances collagen degradation is likely to take place particularly within the lysosomal apparatus after phagocytosis of the fibrils. We propose that this process involves the following steps: (i) recognition of the fibril by membranebound receptors (integrins?), (ii) segregation of the fibril, (iii) partial digestion of the fibril and/or its surrounding noncollagenous proteins by matrix metalloproteinases (possibly gelatinase), and finally (iv) lysosomal digestion by cysteine proteinases, such as cathepsin B and/or L. Modulation of this pathway is carried out under the influence of growth factors and cytokines, including transforming growth factor β and interleukin 1α.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Si x N y , thin layers were analyzed by AES, SIMS, ISS and RBS. A comparison of the experimental results is made, and the artifacts and characteristics for each experimental method are discussed. It seems that of all these methods, only RBS is suitable for analysing silicon nitride layers.
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  • 3
    ISSN: 1573-5044
    Keywords: Beta vulgaris ; cytoplasmic male sterility ; cytoplast ; gradient centrifugation ; Lolium perenne
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Methods for the isolation of cytoplasts from suspension culture-derived protoplasts of the monocot Lolium perenne (perennial ryegrass) and the dicot Beta vulgaris (sugarbeet) have been determined. After comparing a range of gradients it was found that a discontinuous sucrose/mannitol gradient gave the highest cytoplast yields for both species tested: of the protoplasts loaded onto the gradient, for Beta 〉30% and for Lolium up to 45% could be recovered as cytoplasts. Sufficient protoplasts could be loaded onto the gradient to produce suitable numbers of cytoplasts for use in asymmetric somatic hybridisation experiments. Cytoplasts could be isolated from several suspension cultures of different ages. The cytoplast fraction was recovered from the upper part of the gradient in all cases and was only slightly contaminated (2–8%) with protoplasts. Lolium cytoplasts were small, evacuolate cells with granular cytoplasm. In contrast, Beta cytoplasts were larger and predominantly vacuolate. Both contained mitochondria as determined using fluorescence staining.
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  • 4
    ISSN: 1573-5044
    Keywords: cold treatment ; embryogenesis ; flower-stalk segments ; histology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cold treatment of seeds, obtained from crosses between cultivars ofT. gesneriana L., affects the developmental stage of embryos, which in turn influences the frequency of callus induction and the development of different callus types. Cold-treated, mature embryos and basal segments ofin vitro-derived bulblets, were suitable explants for the initiation of regenerative callus on medium with 2,4-dichlorophenoxyacetic acid. The bulblets were initiated on flower-stalk segments from cold-stored bulbs ofT. gesneriana ‘Christmas Marvel.’ Histological analyses of regenerative callus revealed the regeneration of bulb-like structures. The influences of culture medium, culture conditions, growth regulators and acetylsalicylic acid, an inhibitor of ethylene, on the initiation and establishment of regenerative callus cultures are discussed.
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  • 5
    ISSN: 1573-5044
    Keywords: somatic embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of gelling agent and abscisic acid on the morphogenetic response of seed-derived callus cultures of Poa pratensis L. were investigated. On medium solidified with Gelrite, the regeneration frequency of the calluses was twice as high as compared to agar-solidified medium. The average number of green shoots per regenerating callus was not influenced by the type of gelling agent used. When abscisic acid was added to the differentiation medium only, or to both the differentiation medium and the regeneration medium, the percentage of calluses with somatic embryos or embryo-like structures increased (up to 29.6%) as compared to the control (16.4%). The plant formation frequency, however, was not affected by abscisic acid.
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  • 6
    ISSN: 1572-9699
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 7
    ISSN: 1615-5947
    Keywords: Carotid endarterectomy ; venous patch angioplasty ; arterial rupture ; angioplasty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Two cases of vein patch blowout were observed five and seven days after carotid bifurcation endarterectomy with patch angioplasty. Both patients died in spite of emergency reoperation. One patient developed respiratory failure with subsequent fatal cardiac arrest seven days after reoperation; the other died of extensive hemispheric infarction on the fifth postoperative day. At reoperation both ruptures were found to be located in the middle of the patch whereas the suture lines were intact. Both patients were hypertensive. In the first case, an accessory saphenous vein retrieved from the calf had been the only venous material available for the patch, while the other patient had varicose veins in the contralateral leg. Pathology revealed central transmural tissue necrosis in one of the disrupted patches. A review of the literature regarding morphologic alterations of free vein grafts placed within the arterial circulation as well as hemodynamics in patched arterial segments may provide additional insight as to the inherent benefits and risks of vein patch angioplasty after carotid endarterectomy. When considering vein patch angioplasty, particular attention should be directed to the gross aspect of the vein to be used as well as to any antecedent history of phlebitis.
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  • 8
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 20 (1993), S. 233-242 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Ion scattering spectroscopy (ISS) is an established technique for the analysis of atomic species in the outermost atomic layer of a solid surface. Owing to the erosive action of the primary ions, a continued experiment can show the variation of these elemental concentrations in the subsurface layer, just as in depth profiling with AES or XPS and ion sputtering. When used in this ‘depth profiling’ mode, large numbers of spectra are generated that call for automatic processing and interpretation.A complete set of software routines is described that is tailored to the specific aspects of ISS and runs on a personal computer. It allows for on-line, real-time peak detection and identification, as well as for background elimination and peak intensity determination, even in the case of strongly overlapping peaks. The employed strategy is quite general, so that the essence of these routines could easily be adapted to other spectroscopic techniques. The entire procedure is illustrated by a concrete analysis of a photographic material.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 25 (1997), S. 177-190 
    ISSN: 0142-2421
    Keywords: LEIS ; surface segregation ; surface thermodynamics ; EAM ; single crystal surfaces ; iron ; platinum ; intermetallic compounds ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Low-energy ion scattering (LEIS) was used to study the surface composition of a Pt80Fe20(111) alloy surface as a function of temperature. From 700 K onwards, high enough for sufficient atomic mobility to attain equilibrium, the surface consists of nearly pure Pt. These results agree completely with the results from LEED I/V analysis by Beccat et al. [Surf. Sci. 238, 105 (1990)], who also evidenced a monotonic concentration profile over the three top layers, slight relaxations between those layers and a (2×2) superstructure caused by an ordered atomic arrangement in the second layer.Simple expressions for the entropy changes upon segregation in ordered alloys combined with constant pairwise bond energies clearly appear to be inadequate to describe the observed experimental facts. Even when combined with Monte Carlo simulations, the constant bond energies fail to correctly reproduce the results. Only when the Monte Carlo method is combined with the more refined (modified) embedded atom method (MEAM) for energy description of an alloy is satisfactory agreement with experiment obtained. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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