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  • 1
    ISSN: 1540-8191
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Treatment of glutaraldehyde-fixed pericardium with L-glutamic acid and storage in bacteriostatic preservatives (paraben) stably antagonizes free, reactive aldehyde groups within the fixed bioprosthetic heart valve tissue. In 63-day subcutaneous implants in rats, the calcification rate of this treatment (13.3 ± 2 mg calcium/g wt tissue) was markedly reduced as compared to conventionally treated tissue (169 ± 24 mg/g; p 〈 0.05). To test the influence of tissue released toxic aldehdyes on spontaneous endothelial cell ingrowth in vivo, vascular grafts (8-cm long, 6-mm diameter) from fixed pericardium treated with L-glutamic acid were interposed into the carotid arteries in ten sheep. They were compared to grafts from conventionally treated pericardium implanted at the contralateral side. Following 3 months of implantation, planimetry revealed 49%± 20% of the surface of conventionally preserved pericardium to be covered with red thrombus, but only 12%± 5% in L-glutamic acid treated pericardium (p 〈 0.05). The ultrastructural findings of a closed endothelial cell layer on the graft surface reveals the new technique to be a promising approach towards increased biocompatibility of aldehyde-fixed bioprosthetic heart valves.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiac surgery 7 (1992), S. 0 
    ISSN: 1540-8191
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In this in vitro study, the growth properties of cultured endothelial cells on conventionally treated pericardial valve material were measured. These data were compared to endothelial cell proliferation on an alternatively treated valve material. This alternative preservation procedure was developed in order to bind free, residual glutaraldehyde in the valve tissue by reaction with L-glutamic acid. In order to optimize endothelial cell attachment and proliferation, fibronectin and fibrillar collagen type I were tested as surface precoating substances. Cell viability of the seeded cells was evaluated by means of proliferation kinetics, antithrombotic activity, and morphological appearance. Endothelial cell death occurred within the first 2 days after seeding on conventionally treated valve tissue, independent of the type of precoating. On alternatively treated tissue, regular endothelial cell proliferation was observed. Precoating with fibrillar collagen markedly increased endothelial cell attachment and proliferation as compared to fibronectin. Maintenance of antithrombotic activity of the seeded cells was proven by regular release of prostacyclin.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Bingley : Emerald
    Team performance management 4 (1998), S. 177-185 
    ISSN: 1352-7592
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Economics
    Notes: Surveys show that the results of top-down oriented Business Process Reengineering projects often are to be questioned because of implementation problems due to internal resistance to change. Bottom-up oriented Continuous Improvement projects on the other hand experience typically a lack of strategic orientation and do not necessarily improve the enterprise process system as a whole. The MOTION (MOdel for Transforming, Identifying and OptimiziNg core processes) approach developed in a European Union project provides a method to combine the strengths of the top-down approach of business process reengineering with the advantages of the bottom-up oriented continuous improvement process to create well balanced processes to meet customer requirements. The MOTION guidelines were developed by a consortium of European industrial companies and universities.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Mammals have been cloned from adult donor cells. Here we report the first cases of mitochondrial DNA (mtDNA) heteroplasmy in adult mammalian clones generated from fetal and adult donor cells. The heteroplasmic clones included a healthy cattle equivalent of the sheep Dolly, for which a lack of ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Microchimica acta 104 (1991), S. 157-166 
    ISSN: 1436-5073
    Keywords: chemiluminescence ; bioluminescence ; clinical applications ; chemiluminous immunoassays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Luminescent phenomena are widespread in nature and found in glow worms, luminous fish, and bacteria, when metabolic energy is partly converted to cold light, and in plants. Most of these phenomena can be explained by chemiluminescence. Chemiluminescence is characteristic for a variety of organic compounds oxidizable by H2O2. In those chemiluminescence reactions light is produced by oxidation of an aromatic compound (usually luminol or lucigenin) in the presence of H2O2 by a peroxidase. Bioluminescence, a subset of chemiluminescence, may be classified in four different forms: pyridine nucleotide linked in bacteria occurring with coupling of a redox and luciferase reaction; adenine nucleotide linked in fireflies in which oxygen, ATP and luciferin react under the influence of luciferase; furthermore enzyme substrate linked and photoprotein linked bioluminometric processes are observed in arthropods and in jelly fish. In clinical chemistry chemiluminometric assays based either on direct or coupled reactions utilizing ATP, NAD(P)H, FMNH2 or H2O are used. A variety of methods for substrates and enzymes have been described. Furthermore the application of chemiluminometry for the detection of cell functions is of relevance for clinical research. The testing of fertility and of chemosensitivity will be discussed as practical examples. The most promising field are the chemiluminesence immunoassays for measurement of hormones and proteins, since these tests are—at least—sensitive and specific as radioimmunoassays. For detection luminometers with sensitive photomultipliers are used; either the counts at the maximum (peak measurement) are detected or the light intensity is integrated during a certain time period.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Microchimica acta 133 (2000), S. 69-73 
    ISSN: 1436-5073
    Keywords: Key words: Secondary neutral mass spectrometry; surface analysis; instrumental development.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract.  The design and the specifications of a prototype instrument for the electron gas version of secondary neutral mass spectrometry SNMS which will optionally enable measurements with X-ray induced photoelectron spectroscopy XPS, too, are described. By operating the SNMS plasma inside an ultra high vacuum vessel interfering signals from residual gas species are reduced to the level of the mass independent background. The influence of varying angular distributions of sputter-ejected neutrals at low ion energies for sample bombardment can be widely reduced by an oblique take-off for the postionized particles. First examples of SNMS-studies with the new system reveal a detection power well below 1 ppm. Analytically difficult elements as C or O become quantitatively detectable down to a level of several 10 ppm.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We have produced a cell line which lacks the protein tyrosine kinase JAK1 and is completely defective in interferon response. Complementation of this mutant with JAK1 restored the response, establishing the requirement for JAK1 in both the interferon-& alpha;/& beta; and ...
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The 9-27 gene promoter is inducible by IFN-y as well as IFN-a and -p10. Significant constitutive expression from this promoter precluded a drug-selection protocol. Accordingly, a clone of cells (2C4) expressing the simple cell-surface marker CD2 (ref. 11) (normally expressed only on T ...
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Planta 195 (1994), S. 10-16 
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Cell cycle regulation ; Flow cytometry ; Quiescent centre ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mechanism by which the rate of cell proliferation is regulated in different regions of the root apical meristem is unknown. The cell populations comprising the root cap and meristem cycle at different rates, proliferation being particularly slow in the quiescent centre. In an attempt to detect the control points in the cell cycle of the root apical meristem of Zea mays L. (cv. LG 11), quiescent-centre cells were stimulated to synthesise DNA and to enter mitosis either by decapping or by immersing intact roots in an aqueous 3,3-dimethyl-glutaric acid buffer solution. From microdensitometric and flow-cytometric data, we conclude that, upon immersion, the G2 phase of the cell cycle of intact roots was shortened. However, when 50 μM abscisic acid (ABA) was added to the immersion buffer, parameters of the cell cycle were restored to those characteristic of intact roots held in a moist atmosphere. On the other hand, decapping of primary roots preferentially shortened the G1 phase of the cell cycle in the quiescent centre. When supplied to decapped roots, ABA reversed this effect. Therefore, in our model, applied ABA retarded the completion of the cell cycle and acted upon the exit from either the G1 or the G2 phase. Immersion of roots in buffer alone seems to trigger cells to more rapid cycling and may do so by depleting the root of some ABA-like factor.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 343 (1992), S. 137-137 
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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