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  • Polymer and Materials Science  (3)
  • Histochemistry  (2)
  • 1
    ISSN: 1432-0878
    Keywords: Jejunum (rat) ; Lactic acid perfusion ; Mucosal hypertrophy ; Histology ; Histochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung An weiblichen Wistarratten wurden die zellulären und strukturellen Veränderungen der Dünndarmschleimhaut nach chronischer MS-Belastung durch 12tägige Dauerinfusion ins Jejunum untersucht. Folgende Befunde wurden erhoben: 1. Die MS-Belastung führt in Abhängigkeit von der Konzentration zur Reduktion des Glukosetransports. 2. Die Funktionsstörung ist bedingt durch Enzymaktivitätsverlust. 3. Die Reduktion betrifft alle enzymhistochemisch untersuchten Aktivitäten; sie zeigt, daß alle Zellkompartimente des Epithels beeinträchtigt sind. 4. Qualitative Abweichungen des Reaktionsmusters treten nach MS-Belastung nur beim Saure-Phosphatase-Nachweis auf. Sie sind gekennzeichnet durch Schwund der Markierbarkeit lysosomaler Granula und Auftreten einer schwachen, diffusen cytoplasmatischen Aktivität. 5. Die Schleimhaut unterliegt einer von der MS-Konzentration abhängigen Transformation mit Verschiebung der Zottenhöhen und Kryptentiefen. Sie wird begleitet von einer gesteigerten mitotischen Aktivität als Folge erhöhter Zellexfoliation an der Zottenspitze. Es handelt sich bei dieser Veränderung somit um eine Schleimhauttransformation vom hyper-regeneratorischen Typ. Ihr Initialstadium ist eine Hypertrophie, ihr Endstadium die zottenlose Schleimhaut mit stark veränderten Krypten. Das Endstadium wird unter MS-Belastung nicht ausgebildet, da geringe Konzentrationssteigerungen zu lokaler Gewebsschädigung und Darmperforation führen. 6. Das MS-Modell ist wegen seiner geringen experimentellen Breite ungeeignet für die biochemische Nacharbeitung der bei der einheimischen Sprue beobachteten cytochemischen Epithelveränderungen.
    Notes: Summary Cellular alterations and mucosal changes in zonation of the small intestine have been studied after prolonged perfusion (12 days) with lactic acid in the rat. These investigations were carried out with cytochemical methods using marker enzymes to study in detail the different stages of mucosal transformation of the hyperregenerative type. Results. 1. Lactic acid produces a dose-dependent reduction in glucose absorption and this is due to alterations of the absorptive epithelium. 2. The normal zonation of the small intestinal mucosa is changed. The degree and pattern of the alterations is dose-dependent. Mucosal hypertrophy—i.e. increase of villus height, crypt length and mitotic activity—is the initial stage of this process. 3. Both, cellular alterations and mucosal changes in zonation are the expression of strong compensatory activities in response to predominantly intraluminal stress. The relationship between mucosal hypertrophy after intestinal resection and mucosal transformation of the hyperregenerative type as induced by lactic acid infusion is discussed. 4. In view of its very limited experimental range the lactic acid model cannot be recommended for the study of the epithelial changes in mucosal transformation at a biochemical level.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1591-9528
    Keywords: Small intestine ; Mucosal atrophy ; Histochemistry ; Transportstudies ; Malabsorption ; Dünndarm ; Schleimhautatrophie ; Histochemie ; Transport-studien ; Fehlresorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die Fähigkeit des Dünndarms, die Resorptionskapazität unter bestimmten Belastungen kompensatorisch zu vergrößern, ist bekannt. Andererseits fehlen Untersuchungen zum Verhalten der Dünndarmschleimhaut nach partiellem Ausschluß aus der Passage, bei dem mit einem gegensinnigen Anpassungsvorgang zu rechnen wäre. In der vorliegenden Arbeit wurde der Einfluß einer „Inaktivierung“ durch eine segmentale Ausschlußoperation auf die Jejunalschleimhaut der Ratte morphologisch, morphometrisch, histochemisch und mit Hilfe von Transportstudien untersucht, um dieser Frage nachzugehen. 2 Monate nach Ausschaltung der Jejunalschlingen zeigte sich eine Atrophie der Schleimhaut. Bei dieser Atrophie handelte es sich um eine echte Atrophie, die durch eine Abnahme von Zottenhöhe, Mucosastärke und mitotischer Aktivität gekennzeichnet war. Das cytochemische Reaktionsmuster des Resorptionsepithels war weitgehend unverändert. Lediglich bei 3 Tieren mit sehr ausgeprägter Schleimhautatrophie war eine leichte, generalisierte Abnahme der Enzymaktivität feststellbar. Die Resorptionskapazität war ebenfalls hochsignifikant reduziert. Dabei bestand eine gute Korrelation zwischen Abnahme von Zottenhöhe und Glucoseresorption. Die Ergebnisse dieser Studie zeigen die Bedeutung einer „physiologischen“ Belastung für die strukturelle und funktionelle Integrität der Dünndarmschleimhaut.
    Notes: Summary The ability of the small intestine to increase its absorptive capacity as a compensatory response to different types of stress is well recognized. However, no precise information is available about the response of the small intestine when it is partially excluded. A study therefore was undertaken to investigate the influence of such an exclusion on the small intestinal mucosa in rats. In-vivo-transport-methods, morphological, histochemical and morphometric techniques were used. It was found that the small intestinal mucosa of the excluded jejunal loop had become atrophic 2 months after the operation. This atrophy was a true atrophy and characterized by a decrease in villus height, mucosal thickness and mitotic activity. However, the cytochemical pattern of the absorptive epithelium was unchanged apart from 3 animals with most pronounced mucosal atrophy in which there was a slight, but generalized decrease in enzymatic activities. Functionally, there was a highly significant reduction in transport capacity and this was related to the decrease in villus height as shown for glucose. The findings of this study demonstrate the importance of a normal functional load for the preservation of the small intestinal mucosa with respect to both structure and function.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 193-203 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Noncrosslinked copolymers of hydroxyethyl methacrylate (HEMA) with ethyl methacrylate (EMA) were prepared and investigated as candidate materials for reverse osmosis membranes. Water and salt flux were calculated from the results of osmosis experiments, compared with cellulose acetate and found to be somewhat smaller. The mobility of water varies by several orders of magnitude between a high flux cellulose acetate membrane and a low flux HEMA-EMA membrane.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 15 (1977), S. 923-944 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Two models, one for materials possessing a well-defined reference state (solid-like behavior, model S), the other for materials lacking such reference (liquid-like behavior, model L) were tested with the aid of experimental data obtained in various strain histories in simple tension on an uncrosslinked styrene-butadiene rubber (SBR) gum rubber over the temperature range from -20 to 23°C.The models resulted from the introduction of the nonlinear n-measure of strain into the Boltzmann superposition integral. Both gave excellent predictions of the response of the SBR to step and to ramp functions of strain. Published data on the response of polyisobutylene to an exponential stretch ratio excitation were in similarly good agreement with both models. Sensitive tests in which small deformations were superposed on a finite stretch allowed a distinction to be made in favor of model S.In uncrosslinked materials the strain parameter n was found to be small (typically about 0.5) and sensibly independent of temperature in the range investigated. By contrast, in crosslinked rubbers, n is typically between 1 and 2 at room temperature and generally decreases with temperature. The dependence of n on the nature of the material, crosslink density, temperature, and crosslinking conditions was examined.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Letters 3 (1965), S. 965-968 
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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