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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Der Chirurg 68 (1997), S. 215-224 
    ISSN: 1433-0385
    Keywords: Key words: Laparoscopic colorectal surgery ; Port site metastases ; Pitfalls of laparoscopy. ; Schlüsselwörter: Laparoskopische colorectale Chirurgie ; Port-site-Metastasen ; Onkologische Fehler bei der Laparoskopie.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung. Die onkologischen Probleme bei laparoskopisch colorectalen Eingriffen in kurativer Intention bestehen im Auftreten von Port-site-Metastasen, in einer inadäquaten Radikalität, einer Tumorzellverschleppung durch ungeschützte Präparatebergung und unzureichende Operationstechnik sowie Nichtbeachtung technisch-onkologischer Grenzen bei bestimmten Tumorlokalisationen. Die bisher vorliegenden Untersuchungen ergeben eine mehr mechanische Pathogenese der Port-site-Metastasen durch Verschleppung von Tumorzellen in die Trokareinstichstellen über Instrumente, Trokare und Resektionspräparate. Durch entsprechende Vorsichtsmaßnahmen scheint somit eine Vermeidung möglich. Das CO2-Pneumoperitoneum spielt anscheinend eine untergeordnete Rolle bei der Entstehung der Port-site-Metastasen. Die onkologische Radikalität laparoskopischer Eingriffe beim colorectalen Carcinom kann bei fehlenden Langzeitdaten zur Zeit nicht beurteilt werden. Es liegen lediglich vereinzelte Untersuchungen zur Zahl der bei den Eingriffen mitentfernten Lymphknoten vor. Die Anzahl scheint nicht die bei vergleichbaren offenen Resektionen zu erreichen, eine genauere Analyse müßte jedoch die selektionierten Indikationen nach Tumorgröße und -lokalisation berücksichtigen. Die Vielzahl der möglichen Fehler und Gefahren der onkologischen laparoskopischen Chirurgie führt zu der klaren Forderung, daß die Eingriffe nur innerhalb von prospektiven klinischen Studien mit selektionierten Indikationen erfolgen sollten. Eine prospektiv randomisierte Studie für alle Tumorstadien und -lokalisationen ist vor diesem Hintergrund kritisch zu werten.
    Notes: Summary. Oncological problems associated with laparoscopic colorectal surgery with curative intent include port site metastases, inadequate radicality, seeding of tumour cells through unprotected recovery of the surgical specimen, faulty surgical technique, and failure to observe the technical and/or oncological limitations applicable to certain tumour sites. Investigations so far reported reveal a preponderance of mechanical pathogenesis of port site metastases caused by the contamination of trocar entry ports by tumour cells borne on instruments, trocars and resected material. This suggests that appropriate precautionary measures could resolve the problem. It appears that the CO2 pneumoperitoneum plays only a minor role in the development of port site metastases. Owing to a lack of long-term data, the oncological radicality of laparosopic resections for colorectal carcinoma cannot be assessed; merely a few reports on the number of lymph nodes removed during such operations have been published. Nevertheless, it would appear that fewer lymph nodes were removed than with comparable conventional surgery. However, a more accurate analysis needs to take account of the fact that the indication for laparoscopic surgery is determined by the size and location of the tumour. The many potential pitfalls and hazards of oncological laparoscopic surgery make it mandatory that such interventions should be done only within the framework of prospective clinical studies covering limited indications. Randomized prospective studies to cover all tumour stages and sites cannot be recommended.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 128 (1999), S. 123-133 
    ISSN: 1432-1106
    Keywords: Key words Precision grip ; Context-dependency ; Force ; Finger representation ; Motor cortex ; Premotor cortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In three monkeys trained to finely grade grip force in a visuomotor step-tracking task, the effect of the context on neuronal force correlates was quantitatively assessed. Three trial types, which differed in force range, number, and direction of the force steps, were presented pseudo-randomly and cued with the color of the cursor serving as feedback of the exerted force. Quantitative analyses were made on 85 neurons with similar discharge patterns in the three trial types and significant linear positive (54 cells) or negative (31 cells) correlation coefficients between firing rate and force. An analysis of covariance (ANCOVA) showed that the population slopes for 2-step were steeper than for 3-step trials. Another ANCOVA at the population level, computed on the differences in firing rate and force between force steps, persistently disclosed a significant effect of trial type. For the first two force steps, the differences in firing rate were significantly larger in the 2-step than in the 3-step increase trials. Further analyses revealed that neither the force range nor the number of steps was a unique factor. A small group of neurons was tested in an additional trial series with a uniform cue for all three trials, leading to either a loss of context-dependency or to unexpected changes in firing rate. This demonstrates that the cue color was an important instruction for task performance and neuronal activity. The most important findings are that the context-dependent changes were occurring ”on-line”, and that neurons displaying context-dependency were found in all three lateral premotor cortex hand regions and in the primary motor cortex. Finger muscle activity did not show any context dependency. The context-dependent effect leads to a normalization of the cortical activity. The advantage of normalization is discussed and mechanisms for the gain regulation are proposed.
    Type of Medium: Electronic Resource
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