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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 189 (1961), S. 470-472 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] TYREVIOUS work by members of this group has Jt shown that disorders of the flow of blood through both large and small blood vessels appear related to induced or spontaneous electrical currents or their related electrical potential differences in either the vessel wall or surrounding tissues1"3. ...
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 215 (1967), S. 1494-1494 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The electrodes were carefully cleaned to ensure the absence of any oxides or other impurities on their surfaces, and their spontaneous potentials were measured in normal (0.9 per cent) saline solution. In the first series of experiments four electrodes of the same metal were inserted through side ...
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  • 3
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 1 (1973), S. 417-436 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Additional Material: 16 Ill.
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  • 4
    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: Polytetrafluoroethylene surfaces have been treated to reduce thrombogenicity in order to make them suitable for use in prosthetic devices that come in contact with blood. This was done by first etching the surface with potassium in liquid ammonia to produce double bonds and then using these double bonds as sites for grafting on polyacids or as sites for chemical reactions. Tubes so treated were tested for thrombo-genetic activity by implantation in the thoracic aorta or inferior vena cava of dogs. These tests showed that the thrombogenicity of a polytetrafluoroethylene surface can be reduced by attaching negatively charged groups provided the surface concentration of these groups is not too high (order of 1-2 × 10-6 equivalent per cm2 geometric area) and provided the distribution of these groups is uniform. Sulfonic acid groups obtained by chlorosulfonation and carboxyl groups attached by grafting tert-butyl crotonate and hydrolyzing to crotonic acid were effective. Long chains of poly(acrylic acid), poly-(ethylenesulfonic acid), and poly(vinyl alcohol) sulfate were less effective.
    Additional Material: 2 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 13 (1979), S. 937-956 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Dacron velour and knit prostheses were compared with respect to long-term patency when used as canine aortic implants. These grafts were rated, according to the average numerical value of six equally weighted criteria, in decreasing order of performance: velour I, velour II, circular knit III, velour IV, circular knit V, warp-knit VI, warp-knit VII and VIII, warp-knit IX and warp-knit X. In general, compacting and crimping methods using halogenated hydrocarbons produced the least successful grafts. Grafts of identical brand but compacted and crimped by different methods exhibited different patencies. No true healing of any of the grafts was observed. Layered deposits of inner fibrous capsule were formed at rates and thicknesses c a acteristic for each type of graft employed. A functioning Dacron femoral-popliteal bypass removed from a human after 9 months exhibited inner and outer fibrous capsules similar to those from canine implants.
    Additional Material: 5 Ill.
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  • 6
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Evidence is presented for the view that intravascular thrombosis proceeds via an electrochemical mechanism. It is strongly substantiated by some recent work on electrical wire thrombosis. These experiments show that thrombosis occurs on noble metal electrodes at potentials more positive than 0.3 v (NHE) but tends not to occur on electrodes more negative than this interfacial potential. Further, the same factors which prevent intravascular thrombosis are shown to prevent thrombosis on electrodes maintained at all potentials up to + 1.0v. Thus occurrence or prevention of thrombosis appears related to electrical and electrochemical properties of both blood and blood vessel wall. Methods for the determination of these properties are described and experimental results briefly presented. The studies have proved useful in establishing criteria for the selection of metal and plastic vascular substitutes. A combination of several electrochemical and biophysical criteria have been discovered which aid in the selection of nonthrombogenic vascular substitutes. Unfortunately not all metals which satisfy anti-thrombotic electrochemical criteria are suitable. Many, including magnesium, have cellular and proteolytic destructive characteristics. Certain metals and electrically treated Teflon tubes do not suffer from this defect and have proven useful in preliminary testing.
    Additional Material: 10 Ill.
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  • 7
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Knowledge of the characteristics of the blood-intima interface is important because it leads to information concerning (a) the normal antithrombotic mechanism (b) nature of interreactions between blood and intima (c) testing and selection of vascular wall substitutes which are antithrombotic and inhibit clotting. A technique for obtaining the electrical interfacial characteristics of blood vessel walls is by measuring streaming potentials. Experiments described in the present work are extensions of original in vivo streaming potential measurements. In vitro streaming potentials were measured across fresh canine aortae and carotid arteries using Krebs saline serum substitute, logarithmically varying both internal and external electrolyte concentrations. Positive streaming potentials were measured indicating that the blood vessel wall is negatively charged. Streaming potentials increased linearly with increasing flow rate, decreased with increasing internal electrolyte concentration, decreased with increasing external electrolyte concentration, and reversed, becoming positive, with aging of exteriorized artery. Thus the electrical characteristics of the blood vessel wall are dependent on an ionic balance between the blood vessel wall, flowing blood stream, and external environment. The information demonstrates the importance of electrochemical and physicochemical phenomena in the structure and function of the vascular interface and helps explain in vivo conditions conducive to or inhibitory of intravascular thrombosis.
    Additional Material: 12 Ill.
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  • 8
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Additional Material: 7 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 6 (1972), S. 489-498 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In previous studies from our laboratories, it was shown that metals and alloys which register negative potentials in blood vs. the normal hydrogen electrode (NHE) tend to be antithrombogenic, while those with positive potentials are invariably thrombogenic. Of the metals, only the corrodible ones fall in the first group and the noble ones in the second. Blood compatible metals appear to be essential for some types of medical devices. This paper deals with a novel approach of maintaining an implanted metallic prostheses at a negative potential. A copper vascular prostheses in a dog was made the cathode in a polarizing circuit, which in addition consists of a smal mercury battery, a resistor and an auxiliary electrode. Such experiments were conducted in three animals, and the potentials ranged from -60 to -160 mV/NHE. The three dogs were sacrificed after 6, 8, and 14 days and the tubes were examined. All tubes were free of thrombus deposits; minimal junctional thrombi were found. Two copper tubes with no polarizing circuit and registering positive potentials were occluded after 8 and 14 days, respectively. Histologic and electron-microscopic studies of the thrombus deposits in tubes at spontaneous potentials and of the junctional thrombus deposits in the tube at negative potentials showed similar structures. The present experiments further confirm the view that the potential across the conductive material-blood interface is a more basic parameter than the chemical nature of the surface in determining its blood-compatible characteristic.
    Additional Material: 3 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 9 (1975), S. 547-560 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Glow discharge treated (GDT) inorganic materials are sterile and free of all organic contaminants. Such materials implanted in the canine inferior vena cava often demonstrate significant thromboresistance. Standard Pyrex glass tubing was GDT in argon to provide a surface free energy above 70 dynes/cm, slight surface negativity, and other surface-physical modifications of its interface. Chromic acid cleaned lengths of the same tubing, and short segments whose edges were not fire-polished were used as controls. Upon canine implantation, the in vivo results were similar in independent surgical laboratories. The glass was implanted as 1.4 cm long rings or as 5 cm long tubes in separate medical centers according to different protocols. GDT specimens remained patent; all controls accumulated thrombi. A remarkably pure, low critical surface tension, labile protein coating covered all cylindrical lumens after 2 hr in vivo. This coating diminished within 2 weeks and was essentially absent after 480 days, even though scanning EM showed evidence of a micron thick luminal film, probably eroding glass. No emboli were found in the implant animal's kidney or lungs at any stage.
    Additional Material: 9 Ill.
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