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  • 1
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    German Medical Science GMS Publishing House; Düsseldorf
    In:  124. Kongress der Deutschen Gesellschaft für Chirurgie; 20070501-20070504; München; DOC07dgch7761 /20071001/
    Publication Date: 2007-10-02
    Keywords: ddc: 610
    Language: German
    Type: conferenceObject
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  • 2
    ISSN: 0930-9225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0930-9225
    Keywords: Schlüsselwörter Aortale Eingangsimpedanz ; Windkesselfunktion ; „Wrapping“ ; Key words Aortic input impedance ; windkessel ; “wrapping”
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary A decrease in compliance of the ascending aorta caused by prosthetic replacement or “wrapping” may lead to a partial loss of the arterial Windkessel-function. The following study investigated the effects of this intervention on aortic input impedance.  In 8 pigs, the wall of the ascending aorta was wrapped with a prosthesis. This approach was chosen to minimize additional influence of extended operative procedures on the ascending aorta, like extracorporal circulation, cardioplegia or blood loss. Flow and pressure were recorded before and after the intervention, and following Fourier Transformation, the aortic input impedance was calculated.  Mean pressure, mean flow, and total peripheral resistance were unaltered, while there was a significant increase in blood pressure amplitude and characteristic impedance in response to the “wrapping” procedure. Thus, it becomes obvious that even the loss of elastic properties of the ascending aorta only leads to an increase of left ventricular load.
    Notes: Zusammenfassung Prothetischer Ersatz oder Versteifung der Aorta ascendens durch „Wrapping“ können zu einem teilweisen Verlust der Windkesselfunktion des arteriellen Systems führen. In der folgenden, tierexperimentellen Studie wurde untersucht, welchen Einfluß dieser Eingriff auf das Spektrum der aortalen Eingangsimpedanz hat.  Bei 8 Hausschweinen wurde die Aorta ascendens durch Ummantelung mit einer Prothese versteift. Dieses Vorgehen wurde gewählt, um zusätzliche Einflüsse großer operativer Interventionen an der thorakalen Aorta (extrakorporale Zirkulation, Kardioplegie, Blutverlust) zu vermeiden oder zu minimieren. Vor und nach „Wrapping“ wurden Druck und Fluß in der proximalen Aorta gemessen und die aortale Eingangsimpedanz bestimmt.  Blutdruckamplitude und charakteristische Impedanz stiegen nach dem Eingriff signifikant an, während Mitteldruck, mittlerer Fluß und peripherer Widerstand unverändert blieben. Damit wurde gezeigt, daß bereits der Verlust der elastischen Eigenschaften der Aorta ascendens zu einem meßbaren Anstieg der linksventrikulären Nachlast führt.
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  • 4
    ISSN: 0930-9225
    Keywords: Schlüsselwörter Ischämische Kardiomyopathie –¶linksventrikuläres Myokard – Calcium – FURA-2 ; Key words Ischemic cardiomyopathy – left ventricular myocardium –¶calcium – FURA-2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Objective: In ischemic cardiomyopathy (ICM) alterations of the phenotype of myocyte are responsible for critical changes in the intracellular Ca2+-handling. These changes can substantially influence myocardial performance and favor ventricular arrhythmia. Therefore, we investigated whether and how changes in preload, afterload and frequency effect contractility, diastolic Ca2+-handling and resting tension in isolated human myocardium from patients with ICM.¶ Methods: Small muscle strip preparations (0.5×5.0mm) were obtained from non-failing (NDH, n=11) and from non-infarcted areas of failing human hearts (ICM, n=8). Preparations were loaded with the Ca2+-indicator FURA-2 and mounted between a force transducer and servomotor (organ bath: 37°C, oxygenated KHS). The influence of stimulation frequency (0.5–3Hz), preload (0.8–1.5L/Lmax) and afterload on force, passive resting tension and diastolic Ca2+-handling was measured.¶ Results: 1) In NDH, peak isometric force was observed at 2Hz. In contrast, the ICM-myocardium developed maximum isometric force at 1Hz. At higher stimulation rates twitch tension was significantly reduced in ICM (p〈0.0001). 2) Diastolic Ca2+-levels were elevated (p〈0.0001) at higher stimulation frequencies (〉1.5Hz), associated with parallel increase of diastolic resting tension in ICM (p〈0.0001). 3) With increasing preload, force increased in NDH- and in ICM-myocardium. No significant difference in active force generation was observed (n.s.). 4) Passive resting tension was considerably elevated in ICM (p〈0.0001). 5) During shortening, diastolic Ca2+-levels were significantly elevated in ICM (p〈0.0001).¶ Conclusions: The function of the Frank-Starling-Mechanism is maintained in ICM, whereas a negative force-frequency relationship and a disturbed diastolic Ca2+-homeostasis, which is associated with alterations in resting tension, may contribute to the impairment of myocardial performance in end-stage ischemic cardiomyopathy.
    Notes: Zusammenfassung Bei dem Krankheitsbild der ischämischen Kardiomyopathie (ICM) kommt es zu Phänotypenveränderungen der Myozyten, die zu kritischen Veränderungen der intrazellulären Ca2+-Homöostase führen können. Diese Veränderungen können die Kontraktilität des Herzens maßgeblich beeinflussen und Rhythmusstörungen begünstigen. Am Modell des isolierten menschlichen Myokards prüft die vorliegende Untersuchung Kontraktionsverhalten, diastolischen Ca2+-Haushalt und Ruhekraft unter dem Einfluß der Vorlast, der Nachlast und der Frequenz.¶ Methoden: Muskelfaserpräparate (0,5×5,0mm) wurden aus der infarktfreien Zone linksventrikulären Myokards aus ICM-Empfängerherzen (n=8) und aus normalen Spenderherzen (n=11) exzidiert, mit dem Calciumindikator FURA-2 geladen, auf optimale Länge (Lmax) vorgedehnt und elektrisch stimuliert (1Hz, 37°C, oxygenierte Krebs-Henseleit-Lösung). In Abhängigkeit der Vorlast (0,8–1,05L/Lmax), der Nachlast (Verkürzung gegen eine definierte Kraft) und der Frequenz (0,5–3Hz) wurden die aktive Kraftentwicklung, die passive Ruhespannung und intrazelluläre Calciumtransienten unter isometrischen und isotonen Bedingungen gemessen.¶ Ergebnisse: 1) NSH entwickelt die maximale Kraftamplitude bei 2Hz, ICM hingegen bereits bei 1Hz. Höhere Frequenzen führen bei ICM zu einem signifikanten Abfall der Kraft (p〈0,0001). 2) Diastolische Calciumkonzentrationen und Ruhespannungen sind bei Frequenzen 〉1,5Hz bei ICM signifikant erhöht (p〈0,0001). 3) Die Erhöhung der Vorlast führt bei NSH und bei ICM zu ähnlichen Kraftanstiegen (n.s.). 4) Die passive Ruhedehnungskurve ist bei ICM signifikant steiler (p〈0,0001). 5) Eine reduzierte Nachlast führt bei ICM zu einer massiven Calciumüberladung des Cytosols (p〈0,0001).¶ Schlußfolgerung: Im Endstadium der ischämischen Kardiomyopathie bleibt in primär infarktfreien Myokardbezirken die Funktion des Frank-Starling-Mechanismus erhalten. Eine invertierte Kraft-Frequenz-Beziehung und Störungen der diastolischen Ca2+-Homöostase, die mit Veränderungen der passiven Ruhespannung verbunden sind, könnten jedoch nach den vorliegenden Befunden für das gestörte Kontraktionsverhalten des Herzens bei ICM von entscheidender Bedeutung sein.
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  • 5
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Although several clinical studies have shown that increased serum concentrations of protein S100B predict ischaemic brain damage after cardiac surgery, S100B may also be released from the heart or other injured tissue. We therefore investigated the correlation between serum S100B levels and those of the specific cardiac marker troponin I in order to assess the cerebral vs. extracerebral origin of S100B. In 64 cardiac surgical patients, serial blood samples were drawn for the measurement of S100B and troponin I before surgery and for seven days after surgery. Neurological function was assessed before with the National Institutes of Health Stroke Scale and the Folstein Mini Mental Test. The data show that a sustained increase in serum S100B levels is associated with neurological dysfunction, as witnessed by a positive correlation between S100B values and the results of the neuropsychological tests. In contrast, the early postoperative increased levels of protein S100B derive from cardiac tissue, as shown by the positive correlation between S100B and cardiac troponin I levels.
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  • 7
    ISSN: 1432-2013
    Keywords: Rat tracheal smooth muscle ; Contraction kinetics ; Length vibration ; Actin myosin interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The tension increase after onset of electrical stimulation (30 Hz square wave; 1.65 ms pulse duration) and after the cessation of inhibiting length vibration (frequency 100 Hz sinus; amplitude 6% of the muscle length) was analysed in the isolated rat tracheal smooth muscle. In the first experimental series, tonic contraction was interrupted by a 2 s vibration applied 4–256 s after a preceding stimulation. In the second series, the onset of force development was delayed by a long-term vibration stopping 6–258 s after the commencement of a simultaneously performed electrical stimulation. In both the experimental series tested, the time course of post-vibration tension recovery showed an initial fast and a subsequent slow component. The former reflects the kinetics of cross-bridge reattachment and the latter those of the normal actin-myosin interaction cycle. The time constants of both these components reached a minimum of 0.58±0.04 s (fast) and 3.49±0.28 s (slow component) when the vibration stopped 18 s after the start of stimulation. Both values increased to 1.29±0.15 s and 9.98±1.17 s after a preceding stimulation of 256 s. These changes in the time constants may reflect the slowing of cross-bridge action under prolonged contraction. Such variations in the time constants of post-vibration tension recovery occurred without any corresponding changes in the steady state tension developed after cessation of vibration. These results lend further support to the supposition that different mechanisms might control the rate and extent of smooth muscle contraction.
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  • 8
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The contraction kinetics of rat tracheal smooth muscle were studied by analysing the time course of tension recovery after the cessation of a 2 s length vibration (100 Hz, sinusoidal) in activated preparations. An initial fast component of tension recovery reflects the rearrangement of those crossbridges previously detached by vibration. The subsequent slow component could be related to the kinetics of the regular actin-myosin interaction. Both components still occur independently of the duration and type of activation (electrical field stimulation and 0.1 mM1−1 acetylcholine), the bath temperature (16, 28 and 37° C), and of the functional behaviour of the cell membrane (intact or Triton X-100 skinned preparations). The time constants of post-vibration tension recovery were increased distinctly during prolonged activation, low temperature, and after skinning (lack of calmodulin). The activation enthalpy was calculated according to Arrhenius by using the time constant of the slow component of post-vibration tension recovery. It amounted to 94.7 ±0.6 kJ mol−1 for the intact preparation and 97.2 ±1.0 kj mol−1 for the skinned one (temperature range 16–28° C). These results provide further evidence that vibration affects the contractile system directly and that the kinetics of post-vibration tension recovery reflect the kinetics of actin-myosin interaction.
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  • 9
    ISSN: 1435-1803
    Keywords: Frank-Starling ; mechanism ; heart failure ; normal donor hearts ; dilated cardio-myopathy ; heart transplantation ; skinned fibres
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The Frank-Starling-mechanism (FSM) was analyzed in isolated intact and skinned human left ventricular myocardium obtained from 11 heart transplantations (normal donor hearts (NDH), n=8; dilated cardiomyopathy (DCM), n=11). The new technique to utilize muscle strips from normal donor hearts which were actually implanted is described in detail. Methods I) In electrically stimulated left ventricular trabeculae (37°C, oxygenated Krebs-Henseleit solution, supramaximal, electrical stimulation, frequency 1 Hz) force development was analyzed as a function of muscle length (NDH=8; DCM=11). II) In an additional series left ventricular myocardium was demembranized (“skinned”) by Triton-X-100. At different sarcomere lengths and calcium concentrations corresponding to pCa values of 4.3, 5.5, and 8.0 force development was measured (DCM=11; NDH=9). Results I) Developed force increased up to an optimum as a function of muscle length in intact NDH- and DCM-myocardium. However, the relative increment of developed force after any length step was smaller in DCM than in NDH. Near “Lmax” (muscle length associated with maximum developed force) passive resting tension was considerably elevated in DCM, indicating significantly incresed diastolic stiffness II) In skinned left ventricular DCM- and NDH-myocardium developed force depended on sarcomere length with an optimum near 2.2 μm. However, a reduction of activator calcium concentration from pCa 4.3 to pCa 5.5 produces a smaller percent decline in force at short sarcomere lengths in DCM than it does in NDH. Conclusion the present study shows that except for diastolic stiffness and a smaller relative force increment after any, length step in DCM the Frank Starling mechanism is still present in isolated human left ventricular DCM-as in NDH-myocardium. The current study does not allow to decide whether in skinned myocardium the smaller percent decline in force after reduction of activator calcium concentrations in DCM is caused by an increased calcium sensitivity at short sarcomere lengths or decreased sensitivity at long sarcomere lengths.
    Type of Medium: Electronic Resource
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