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  • Polymer and Materials Science  (4)
  • hypobaric condition  (1)
  • matrix metalloproteinase  (1)
  • 1995-1999  (3)
  • 1980-1984  (3)
  • 1
    ISSN: 1435-1803
    Keywords: Collagen ; cardiac muscle ; endurance training ; hypobaric condition ; mRNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The objective of this study was to examine the effects of prolonged exposure to hypobaric hypoxic condition, physical training and their combination on collagen type I, III and IV gene expression in the ventricles and atria of rat heart. Male rats were assigned to four groups: normobaric sedentary (NS) and trained (NT), and hypobaric sedentary (HS) and trained (HT). Exposure to and treadmill running training in hypobaric condition were carried out in a hypobaric chamber (770–740 mbar, 2250–2550 m). Experimental periods were 10, 21 and 56 days; the groups of 91 days served as recovery groups from experimental settings of 56 days. Exposure to hypobaric condition as such and in combination with endurance training for 10 days increased right ventricular weigth-to-body weight ratio (RV/BW) by 26% (p〈0.001) and 23% (p〈0.01), respectively, when compared to 10NS. RV/BW was significantly increased also in 21HT and 56HT. Left ventricular weight-to-body weight ratio was 13% (p〈0.01) and 14% (p〈0.01) higher in 21HT and 56HT, respectively, than in the respective NS. Right ventricular collagen type III mRNA level was 33% (p=0.065) and 38% (p〈0.01) higher in 10HT than in 10NS and 10NT, respectively. Right ventricular collagen type IV mRNA level was 29% (p〈0.001) higher in 10HT than in 10NS. Relatively slight left ventricular hypertrophy was not associated with significant changes in collagen mRNA levels. Decreased left ventricular subepicardial prolyl 4-hydroxylase activity in 10HS and 10HT suggests transient corresponding decrease in the rate of collagen synthesis. This study shows that combination of endurance training and moderate hypobaric hypoxic condition leads to increased right ventricular collagen type III and IV gene expression associated with right ventricular hypertrophy.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this article we review the synthesis and morphology and the physical and mechanical properties of two-component interpenetrating polymer networks (IPNs) from polyurethane and epoxy polymers; the corresponding pseudo-IPNs and grafted IPNs are also discussed. A comparison was made of full IPNs, pseudo-IPNs, grafted IPNs, and related homopolymers by examining their mechanical properties, mechanical spectra, and electron microscopy on an investigation of the effects of interpenetration or permanent entanglement in the IPN and related systems. This interpenetration has resulted in improved compatibility between the two polymer systems and has caused a decrease in the degree of phase separation. An observed shift in the dynamic glass transition temperatures (Tgs) of the two components which yielded a single IPN Tg further substantiates our results.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two-component interpenetrating polymer networks (IPNs) that contained charge groups in the backbones of the polyurethane and epoxy networks were studied. IPNs that contained opposite charge groups, similar charge groups, no charge groups, and corresponding pseudo-IPNs were prepared. A comparison of mechanical properties, water-resistance data, mechanical spectra, and electron microscopy showed that improved properties and morphologies resulted in IPNs that contained opposite charge groups. Presumably, interactions between the opposite charge groups in the constituent networks resulted in a forced compatibility between the two polymers which decreased the degree of phase separation.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three-component IPN systems made from polyurethanes, epoxies, and poly(methacrylates) containing charge groups in the backbones of the constituent networks have been prepared. Specific attractive forces that occurred among the various networks helped to compatibilize them and aided in the formation of true homogeneous topologically interpenetrating polymer networks. These three-component polymer alloys, including full-IPN's, pseudo-IPN's, and graft-IPN's, were characterized by means of mechanical spectroscopy, electron microscopy, and stress-strain properties. In addition, some adhesion studies were carried out (lap shear strength and peel strength). A comparison of the different types of three-component polymer alloys showed that better properties were generally exhibited by the graft-IPN's and full-IPN's containing opposite charge groups.
    Additional Material: 5 Ill.
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  • 5
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Aus Poly(oxytetramethylen), 4,4′-Bibenzyldiisocyanat, N-Methyldiethanolamin als Kettenverlängerer und Acrylsäure/Polyacrylsäure als Quaternisierungsagens wurden Poly(etherurethan)-Kationomere hergestellt. In aus diesen Kationomeren hergestellten Filmen wurde Pyrrol (15 Gew.-%) in Gegenwart von CuCl2 polymerisiert. Die Filme wurden mittels dynamisch-mechanischer Analyse, Thermogravimetrie und Differentialthermoanalyse charakterisiert. Die elektrische Leitfähigkeit beträgt für den Film ohne Polypyrrol 7.5 · 10-12 Ω-1 cm-1 und mit Polypyrrol 4.5 · 10-6 Ω-1 cm-1.
    Notes: Poly(ether urethane) cationomers based on poly(oxytetramethylene), 4,4′-bibenzyldiisocyanate, N-methyldiethanolamine as chain extender, and acrylic acid/poly(acrylic acid) as quaternization agent were synthesized. Pyrrole (15 wt.%%) was polymerized in films of the ionomer containing CuCl2. The films were characterized by dynamic mechanical analysis, thermogravimetry and differential scanning calorimetry. The electric conductivity of the film without polypyrrole is 7.5 · 10-12 Ω-1 cm-1, while incorporation of polypyrrole increases the conductivity to 4.5 · 10-6 Ω-1 cm-1.
    Additional Material: 2 Ill.
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  • 6
    ISSN: 1432-0428
    Keywords: Keywords Glomerulosclerosis ; matrix metalloproteinase ; tissue inhibitor of metalloproteinases ; obese Zucker rat.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The obese Zucker rat represents a model of obesity combined with insulin resistance and hyperlipidaemia, which over a period of several months develops spontaneous glomerulosclerosis. The present study addressed the question as to whether glomerular sclerosis was associated with alterations in the degradation of matrix components. In the early phase (up to 6 months) glomeruli from obese rats displayed increased total collagen content (+ 64 %) and decreased gelatinolytic activity (− 34 %) as compared to lean control animals. This decline in glomerular gelatinolytic activity was due to a reduction in gelatinase B [matrix metalloproteinase (MMP)-9]. Glomerular MMP-9 mRNA was reduced 4.6 ± 0.6-fold (n = 3; p 〈 0.05), MMP-9 protein was not detectable by Western blotting and MMP-9 activity was considerably suppressed in gelatin zymograms. MMP-2, in terms of mRNA expression and activity, was unchanged. Tissue inhibitor of metalloproteinases (TIMP)-1 mRNA expression, TIMP-1 protein (immunohistochemistry) and TIMP-1 activity (reverse zymography) were enhanced in glomeruli from obese rats, while TIMP-2 mRNA remained unchanged. Moreover, mRNA for the α1 IV collagen chain was 2.1 ± 0.8-fold higher in glomeruli isolated from obese animals (n = 3; p 〈 0.05). These findings indicate that matrix expansion in glomeruli from obese Zucker rats is due to both enhanced synthesis of matrix components as well as reduced degradation by matrix metalloproteinases. Apparently the latter effect is based on a reduction in MMP-9 and up-regulation of its inhibitor TIMP-1. [Diabetologia (1997) 40: 1035–1043]
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