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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Biomedical microdevices 2 (2000), S. 283-294 
    ISSN: 1572-8781
    Keywords: neural prostheses ; MEMS ; polyimide ; electrical stimulation ; implant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Micromachining technologies were established to fabricate microelectrode arrays and devices for interfacing parts of the central or peripheral nervous system in case of neuronal disorders. The devices were part of a neural prosthesis that allows simultaneous multichannel recording and multisite stimulation of neurons. Overcoming the brittle mechanics of silicon, we established a process technology to fabricate light-weighted and highly flexible polyimide based devices. Concerning the challenging housing demands close to the nerve to prevent mechanical induced nerve traumatization, we integrated interconnects to decouple the nerve interface from plugs and signal processing electronics. Hybrid integration with a new assembling technique—the MicroFlex interconnection (MFI)—has been applied for the connection of the flexible microsystems to silicon microelectronics. In this paper, we present different shapes and applications of the flexible electrodes: sieve electrodes for regeneration studies, cuff electrodes for interfacing peripheral nerves, and a retina implant for ganglion cell stimulation. The discussion is focused on electrode and material properties and the hybrid assembly of a fully implantable neural prosthesis.
    Type of Medium: Electronic Resource
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  • 12
    ISSN: 1432-0878
    Keywords: Dentinoenamel junction Structure Mineralization High-resolution electron microscopy Numerical analysis Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The development of dentin and of enamel share a common starting locus: the dentinoenamel junction (DEJ). In this study the relationship between enamel and dentin crystals has been investigated in order to highlight the guiding or modulating role of the previously mineralized dentin layer during enamel formation. Observations were made with a high-resolution electron microscope and, after digitalization, image-analysis software was used to obtain digital diffractograms of individual crystals. In general no direct epitaxial growth of enamel crystals onto dentin crystals could be demonstrated. The absence of direct contact between the two kinds of crystals and the presence of amorphous areas within enamel particles at the junction with dentin crystals were always noted. Only in a few cases was the relationship between enamel and dentin crystals observed, which suggested a preorganization of the enamel matrix influenced by the dentin surface structure. This could be explained either by the existence of a proteinaceous continuum between enamel and dentin or by the orientation of enamel proteins by dentin crystals.
    Type of Medium: Electronic Resource
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  • 13
    ISSN: 1433-0458
    Keywords: Schlüsselwörter Tip-Link-Hypothese ; Lärmschwerhörigkeit ; Schalltrauma ; Tinnitus ; TTS ; Key words Tip link hypothesis ; Noise-induced hearing loss ; Tinnitus ; TTS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Sound overexposure is known to cause damage to cochlear structures and can induce permanent or temporary hearing loss and tinnitus. Perhaps the most sensitive of these structures to sound overexposure are the tip links. In this paper the elecrophysiological effects of pharmacological destruction of the tip links of outer hair cells was investigated. Outer hair cells treated with elastase (20 U/mL) or BAPTA (5 mM) no longer responded to sinusoidal stimuli. In contrast to common belief, transduction channels opened due to loss of tip links. Such opened channels can allow K+ and Ca2+ to enter the cell from the endolymphatic space and could lead to permanent depolarization. This influx of cations caused by loss of tip links, together with the subsequent hair-cell depolarization, might be a source of sensorineural hearing loss and tinnitus associated with acoustic trauma.
    Notes: Zusammenfassung Eine extreme Lärmexposition ist bekannt dafür, Schädigungen des Gehörs hervorzurufen, die sich in permanenter oder temporärer Schwerhörigkeit und Tinnitus manifestieren können. Vor allem die Stereozilien der Haarsinneszellen stellen einen sensiblen Angriffspunkt dar: deren rämliche Ordnung und ihre Verbindungsfilamente (Tip-Links) können zerstört werden. In der vorliegenden Arbeit wurde die Auswirkung einer pharmakologischen Zerstörung der Tip-Links auf das elektrophysiologische Verhalten der Zelle untersucht. Es zeigte sich, dass die behandelten äußeren Haarsinneszellen nicht mehr mechanosensitiv für nasische Stimuli waren, was die Wichtigkeit der Tip-Links bei der Reiztransduktion unterstreicht. Entgegen der allgemeinen Erwartung gingen die mechanoelektrischen Transduktionskanäle aber in einen offenen Zustand über. Durch die permanent offenen Kannäle strömen dauerhaft hauptsächlich K+- und Ca2+-Ionen aus der Endolymphe in die Zelle ein und führen zu einer Depolarisation. Dieser durch den Verlust der Tip-Links verursachte Einstrom von Kationen und die Depolarisation der Zelle können ein Teil der Ursache einer dem Schalltrauma begleitenden Symptomatik wie Innenohrschwerhörigkeit und Tinnitus sein.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für Kardiologie 89 (2000), S. 362-363 
    ISSN: 1435-1285
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 15
    ISSN: 1435-1285
    Keywords: Key words Magnetic resonance imaging – coronary angiography – coronary artery bypass grafts – MR – coronary angiography ; Schlüsselwörter Kernspintomographie – Koronarangiographie – koronare Bypassgefäße – MR-Koronarangiographie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Das Ziel der Studie war die kernspintomographische Evaluierung koronarer Bypassgefäße mit der Haste- und Fisp-3-D-Angiographiesequenz unter besonderer Berücksichtigung der distalen Bypassanastomose. Eingeschlossen wurden 29 Patienten mit 74 Bypassgefäßen und insgesamt 91 distalen Anastomosen. Eingesetzt wurden eine 2dimensionale, T-2-gewichtete Turbo-Spin-Echo-Sequenz (Haste) sowie eine 3dimensionale, kontrastmittelunterstützte Angiographiesequenz (Fisp-3-D) in Atemanhaltetechnik. Sowohl mit der Haste- als auch der Fisp-3-D-Sequenz konnten 55 der 58 offenen und 15 der 16 verschlossenen Bypässe korrekt beurteilt werden, die Sensitivität und Spezifität betrug 95% und 94%. Überlegen war die Haste-Sequenz (47/63) der Fisp-3-D-Sequenz (40/63) in der Beurteilung der distalen Anastomosen. Bypasstenosen konnten lediglich in 3 von 8 Fälen diagnostiziert werden. Mit der Kernspintomographie ist mit beiden genannten Sequenzen eine nichtinvasive Evaluierung koronarer Bypassgefäße möglich, wobei die Haste-Sequenz in der Beurteilung distaler Bypassanteile überlegen ist. Eine Verbesserung der Aussagekraft der Methode ist durch den Einsatz von gefäßständigen Kontrastmitteln sowie durch die Kombination mit funktionellen Parametern wie der MR-Flußmessung zu erwarten.
    Notes: Summary The aim of the study was to evaluate the patency of coronary artery bypass grafts (CABG) with the 2D and 3D magnetic resonance (MR) imaging techniques. 29 patients with 74 bypass grafts and a total of 91 distal anastomoses were studied on a 1.5 Tesla scanner using a phased array body coil. A 2D T-2 weighted breathhold turbo spin echo sequence (Haste) and a 3D breath hold contrast enhanced MR angiography sequence (Fisp-3-D) were performed. With the Haste and Fisp-3-D sequences 55 of the 58 patent and 15 of the 16 occluded grafts were recognized; the sensitivity and specifity were 95% and 94%, respectively. With the Haste sequence 74% (47/63) and with the Fisp-3-D sequence 64% (40/63) of the distal anastomoses were seen in good image quality. Only 3 of 8 significant grafts stenoses were detected. The patency of CABGs can be evaluated non-invasively with the Haste and the Fisp-3-D angiography sequences. Better results can be expected with the development of a blood-pool contrast medium and the combination of MR flow measurements with imaging techniques.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für Kardiologie 89 (2000), S. 464-468 
    ISSN: 1435-1285
    Keywords: Key words Cardiac tamponade – cardio-pulmonary resuscitation – retropharyngeal abscess –streptococcus milleri ; Schlüsselwörter Perikardtamponade – kardiopulmonale Reanimation – Retropharyngealabzeß–Streptococcus milleri
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Wir berichten über eine 67jährige Patientin, die im Rahmen einer Perikardtamponade plötzlich reanimationsbedürftig wurde. Die Ergußdrainierung zeigte eine putride Flüssigkeit, aus der Streptococcus milleri isoliert werden konnte. Fremdanamnestisch litt die Patientin schon 4 Tage vor dem Ereignis an einer allgemeinen körperlichen Schwäche, Dyspnoe, Fieber bis 39°C, Halsschwellung und Schluckbeschwerden. In einer CT-Untersuchung zeigte sich eine Entzündungsstraße ausgehend von der rechten Tonsille über das Mediastinum bis hin zum Perikard. Nach operativer Sanierung des retropharyngealen Abszesses heilte die Erkrankung vollständig aus. Das Krankheitsbild der eitrigen Perikardtamponade muß differentialdiagnostisch immer an einem hämatogenen, lymphogenen oder per continuitatem sich ausbreitenden Prozeß denken lassen. Der Erregernachweis im Erguß sowie die typische Anamnese ließen an eine oropharyngeale Ursache denken.
    Notes: Summary We present the case of a 67 year old woman who was resuscitated due to cardiac tamponade. Examination of the pus fluid showed a bacterial infection with streptococcus milleri. Four days before resuscitation the patient experienced weakness, dyspnoe, increased temperature (39° C), swelling of the neck, and pain on swallowing. Using computed tomography, examination revealed an infection extending from the right tonsil to the mediastinum and into the pericardium. After surgery to remove the retropharyngeal abscess, the patient healed well. Therefore, on presentation of a cardiac tamponade, possible hematogenous or lymmphogenous causes or per continuitatem infections should always be considered. In this case the germs in the fluid and the typical patient history indicated an oropharyngeal reason.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    Intensivmedizin und Notfallmedizin 37 (2000), S. 161-162 
    ISSN: 1435-1420
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Clinical oral investigations 4 (2000), S. 126-129 
    ISSN: 1436-3771
    Keywords: Key words Tissue engineering ; Growth factors ; Peptides ; Proteins ; Dental
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  This paper presents a short review of three groups of tools which can be or are used for the tissue engineering of mineralized oral structures: growth factor delivery systems (GFDS) and surface bioactivation with covalent bound peptides or with nanomechanically linked proteins. According to the reported personal experience of the authors, GFDS have to face the following challenging issue before being used routinely in dentistry, e.g., as a tool for reparative dentinogenesis or bone healing: adaptation of the GFDS design to the tissue where it will be implanted in order to deliver the right dose of growth factor (GF) at the right time. The bioactivation of surfaces, for example of dental implants, with covalent bound peptides or nanomechanically linked proteins represents a second innovative way to improve dental health in the future. Here we report on the experimental use of cyclic RGD peptides grafted on polymethylmethacrylate to improve osteoblast adhesion. Furthermore, we show the potential advantage of immobilizing and incorporating collagen I on titanium implant surfaces. These techniques or a combination of them will help to create improvements, for example, of dental implants in the near future. They will also help to promote bone and dentin regeneration.
    Type of Medium: Electronic Resource
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