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  • 1
    ISSN: 0301-0104
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0301-0104
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0304-8853
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physica B+C 98 (1980), S. 197-201 
    ISSN: 0378-4363
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-2307
    Keywords: Venous vessel wall ; Endothelial permeability ; Intimal fibrous thickening ; Cellular fibrous proliferation ; Phlebosclerosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present study examined the intimal reactions of rabbit jugular veins to a stimulus known to elicit arteriosclerotic alteration in the artery wall. Repeated transmural electrical stimulation was applied to external jugular veins of both normo- and hypercholesterolaemic rabbits. Endothelial permeability, as well as changes in intimal architecture, were investigated by electron microscopy. Initially, the veins responded to electrical stimulation with an increased transendothelial transport of horseradish peroxidase (40000 daltons). After application of the stimulation program for 4 weeks, intimal fibrous thickening (33%), cellular fibrous proliferation (50%), and organized mural thrombi were observed. The fibrous thickening was characterized by an abundance of connective tissue matrix and paucity of subendothelial cells. The cellular fibrous proliferate predominantly consisted of myocytes with few interspersed monocytes/macrophages and granulocytes. It resembled intimal plaques induced in carotid arteries by the same method. However, the venous thickenings showed limited size and a more pronounced fibrous response when compared with the arteriosclerotic lesions. The morphological similarities between the observed venous intimal thickenings and the different types of phlebosclerotic manifestations described in the literature, especially intimal proliferations in vein grafts, render the model of electrical stimulation suitable for the elucidation of underlying pathogenic mechanisms.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0942-0940
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Average $${\text{P}}_{{\text{O}}_{\text{2}} }$$ and $${\text{P}}_{{\text{CO}}_{\text{2}} }$$ , local blood flow and pH values in the cerebral cortex of the cat were measured during passive hyperventilation (arterial $${\text{P}}_{{\text{CO}}_{\text{2}} }$$ below 19 mm Hg). At defined intervals tissue samples were taken for metabolite analysis. The object of the study was to correlate the data obtained on the brain surface with metabolic responses. Immediately after the start of hyperventilation blood flow decreased, average cortical tissue pressures of O2 and CO2 fell, and there was a simultaneous rise in cortical pH. At a later stage in the experiment the local blood supply reverted to its resting level. Despite a fivefold rise in tissue lactate level during hyperventilation and a decrease in local O2 pressure on the brain surface to 5–10 mm Hg the degree of phosphorylation of energy rich phosphates was not less than under normal conditions of oxygenation. Our investigations showed no evidence of energy lack in cerebral cortex cells during hyperventilation. Cellular hypoxia and its characteristics are defined. The possible causes of raised tissue lactate levels during hyperventilation despite the lack of evidence of cellular hypoxia are discussed.
    Notes: Zusammenfassung Auf der Großhirnrinde der Katze wurden der mittlere O2- und CO2-Druck, die lokale Hirndurchblutung und der pH-Wert während passiver Hyperventilation (art. CO2-Druck unter 19 mm Hg) fortlaufend gemessen und zu definierten Zeitpunkten Gewebsproben der Hirnrinde entnommen, die auf ihre Gehalte an Metaboliten des energieliefernden Stoffwechsels analysiert wurden. Ziel der Untersuchung war eine Synopsis der auf der Hirnoberfläche gemessenen Daten mit geeigneten Kenngrößen des Energie-Stoffwechsels. Unmittelbar nach Beginn der Hyperventilation sank die Durchblutung, der mittlere kortikale Gewebsdruck für O2 und CO2 bei gleichzeitiger Erhöhung des pH-Wertes. Im weiteren Verlauf des Experimentes erreichte die lokale Hirndurchblutung wieder den Ausgangswert. Trotz eines Anstiegs des Gewebs-Laktatspiegels um das Fünffache während der Hyperventilation und des auf 5–10 mm Hg erniedrigten lokalen O2-Druckes der Hirnoberfläche war der Phosphorylierungsgrad der energiereichen Phosphate nicht geringer als unter normoxyschen Bedingungen. Die Untersuchungen ergeben keinen Anhalt für einen Energiemangel der Hirnrindenzelle bei Hyperventilation. Der Begriff der Hypoxie und ihre Kenngrößen werden für den zellulären Bereich präzisiert. Die möglichen Ursachen des erhöhten Gewebs-Laktatspiegels während der Hyperventilation trotz Fehlens von Zeichen einer zellulären Hypoxie werden diskutiert.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-0584
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0014-4827
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1433-8580
    Keywords: Smooth muscle cells ; Endothelium ; Permeability ; Atherosclerosis ; Peroxidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Repeated weak electrical stimulations of rabbit carotid artery walls with implanted electrodes cause intimal proliferations of smooth muscle cells (SMC) and lead to fribromuscular plaques beneath the anode. If the animals receive a cholesterol-enriched diet the plaques become typical atheromas. The endothelial lining is maintained. The procedure for the production of an atheroma with 11 ± 4 layers of SMC lasts 4 weeks. Addition of the calcium antagonist Flunarizine to the food during the stimulation periods inhibits the growth of the plaque. The inhibition is dose-dependent. Whether the drug inhibits atherogenesis by direct action on SMC or via an effect on permeation of macromolecules through the endothelium has been studied by measurement of (1) peroxidase (MW 40,000 dalton) permeability through the stimulated endothelium of the artery and (2) the inhibitory effects of Flunarizine on cultures of arterial SMC. Endothelial permeability increases for some hours after stimulation mainly beneath the anode. Flunarizine inhibits the permeation of peroxidase through the endothelial lining for the most part by its action on intercellular transport. The drug also inhibits the growth of SMC in mass cultures and clone cultures. The inhibition of proliferation is not specific for SMC. Skin fibroblasts obtained from the same animals as the artery smooth muscle cells are also inhibited in mass cultures and clone cultures. From the results it can be concluded that Flunarizine exerts its inhibitory action not only by its effect on the permeation through the endothelial lining but by a combined action on permeability and proliferation of cells in the artery wall.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1433-8580
    Keywords: Arteriosclerosis ; Argyrophilic cells ; Intimal monocytes/macrophages ; Granulocytes ; Smooth muscle cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In rabbit carotid arteries arteriosclerotic lesions were induced by repeated local transmural electrical stimulations. The sequence of early morphological alterations in the vessel wall and especially the kinetics of leukocytes were examined by transmission electron microscopy. After a stimulation period of only 1 day monocytes and heterophilic granulocytes adhered to the endothelial surface. In the subendothelium mainly beneath the anode, focal amorphous insudates were present together with mononuclear and granulocytic cells. Thereby, the endothelium was maintained as a continuous lining as shown by surface staining with silver nitrate. However, both pattern and size of the endothelial cells were altered in comparison to the controls. Some of the endothelial cells displayed a heavy cytoplasmic silver salt deposition. After 2 days of the electrical stimulation schedule, the first myocytes occurred in the subendothelial space. The mediamyocytes sending pseudopods through the internal elastic lamina still appeared to be in a contractile phenotype. In the 7-day-old proliferative lesion modulated smooth muscle cells were the predominant cell type; only 10%–20% of the subendothelial cells were identified as macrophages and heterophils. This proportion decreased further, and after a stimulation period of 28 days the granulocytes disappeared completely. At this stage of plaque development, the intimal myocyte population mainly consisted of contractile smooth muscle cells and intermediary states between the contractile and modulated phenotype. The insudation, immigration of white blood cells, and subsequent migration and proliferation of myocytes reinforces the view that the initial phases of arteriosclerotic lesions may represent a special form of an inflammatory response.
    Type of Medium: Electronic Resource
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