Development of an in vitro blood flow model to evaluate antimicrobial coatings for blood-contacting devices

Pre-clinical evaluation of novel antimicrobial coatings for blood-contacting devices commonly relies on the performance of animal studies since alternative in vitro models do not adequately represent the interactions between blood, bacteria, and material surfaces as they occur in vivo. To reduce the need of these cost-intensive and controversial animal tests, this project was dedicated to the development of a new model setup that overcomes this limitation and allows in vitro evaluation under in vivo-like conditions. This newly developed model was intended to be directly applied to evaluate recently in-house developed antimicrobial coatings, so-called anchor polymers. Therefore, the project was divided into two parts. The first part of the project focused on the evaluation of the anchor polymer coatings concerning their applicability in blood-contacting devices. For this purpose, the PEGylated styrene-maleic acid copolymers were intensively studied using established laboratory tests. These examinations showed very promising results regarding adsorption and stability on relevant polymer substrates, antimicrobial efficacy, and biological safety of the coatings, thus revealing their great potential for future applications in medical devices. Moreover, this basic characterization was meant to allow a subsequent comparison of the new in vitro model with state-of-the-art in vitro tests. The second part of the thesis focused on the development of the realistic in vitro model. Here, a single-pass flow system realized the implementation of adjustable flow conditions. Furthermore, incubation with freshly drawn human blood provided a physiological nutrient environment and included the influence of an immune response. Staphylococcus aureus were chosen as representative microorganisms, as they are responsible for a majority of device-related blood stream infections. The resulting blood flow model was validated with one anti-adhesive and one contact-killing anchor polymer coating, confirming the model’s ability to differentiate the investigated surfaces. Inflammatory and coagulant blood activation correlated slightly with bacterial coverage, which in turn was strongly dependent on the investigated material surface. Incubation with varying flow conditions demonstrated the model’s capability to reflect the well-documented dependence of bacterial colonization and occurring flow conditions. In contrast to the state-of-the-art in vitro tests, the simultaneous incubation of test surface, bacteria and whole blood allowed the analysis of mutual interactions of the three parameters. Thus, the model represents an excellent method for pre-clinical evaluation of novel antimicrobial coatings for blood-contacting devices

Grundschulpädagogik als empirische Forschungsdisziplin

Der Beitrag prüft die Frage, in welchem Sinne sich die Grundschulpädagogik als empirische Forschungsdisziplin betrachten läßt. Das geschieht zunächst - und mit Defizitbefunden - an Schriften zum theoretischen Selbstverständnis der Grundschulpädagogik; dann werden pädagogisch- psychologische Forschungsarbeiten geprüft, die für sich grundschulrelevante Leistungen beanspruchen, mit dem Ergebnis, daß solche Ansprüche nicht eingelöst werden. Schließlich wird das Thema in konstruktiver Absicht aufgenommen, mit Verweisen auf die Erwartungen, die an eine handlungsrelevante sowie methodisch und theoretisch rechtfertigungsfähige empirische Forschung über die Grundschule, ihre Aufgaben und Probleme, zu stellen sind. (DIPF/Orig.)The author enquires into the question in how far the pedagogics of primary education may be considered a discipline of empirical research. To this end, she first studies writings on the theoretical self-understanding of the pedagogics of primary education - finding deficits in this respect, she then goes on to examine educational-psychological research claiming to be relevant to the field of primary education. The results, however, show that this claim seems not to be supported. Finally, the author points to possible alternative approaches, referring to the expectations, linked to action-oriented empirical research on primary education, its tasks and its problems, - research that can be legitimated both methodologically and theoretically. (DIPF/Orig.

Chronic vascular constrictions and measurements of renal function in conscious rats

Although a tremendous amount of physiologic information has been gained from experiments on anesthetized animals, there is often the question to what extent anesthesia itself, as well as the losses and replacement of fluid that accompany surgical preparations, might have influenced the function being studied. This possible pitfall may apply especially to studies on the kidney because the renal circulation is so exquisitely sensitive to anesthetic agents and changes in fluid balance. Chronic preparations in dogs have been [1] and continue to be used [2] successfully. But the far lesser expense of rats, as well as their common use in physiologic experiments, points up the desirability of a successful chronic preparation in this species. Renal clearances have been performed previously on unanesthetized rats [3, 4], but the methods have not been generally adopted.We here describe a method that can measure renal clearances and extraction of PAH accurately and repeatedly in the same conscious rat over a period of weeks. For our own purposes [5] we also needed a method for constricting blood vessels. The design and construction of a suitable cuff for this purpose, likewise usable in unanesthetized rats, also form part of this report

Zur Präferenz von Noten- oder Verbalbeurteilung - Ein Vergleich Ost- und Westberliner Eltern

"Der Verzicht auf Notengebung und die Einführung der verbalen Beurteilung sind Kernstücke der Grundschulreform der siebziger Jahre, die auf individuelle Förderung aller Kinder, ermutigende Erziehung und Anhebung der Chancengleichheit abzielte". Inzwischen hat sich die verbale Beurteilung in den ersten beiden Grundschulklassen durchgesetzt, die Ausdehnung auf weitere Klassenstufen ist abhängig von der Akzeptanz durch die Eltern. Der Beitrag berichtet über die Ergebnisse eines Berliner Forschungsprojektes, in dem Eltern nach ihrer allgemeinen Einstellung zu Schule und Erziehung und insbesondere nach ihrer Meinung zur Noten- und Verbalbeurteilung befragt wurden. Dabei werden die Ergebnisse bei Ost- und Westberliner Eltern verglichen. (DIPF/Mass.

GFR and the concentration of urine in the absence of vasopressin. Berliner-Davidson re-explored

Robert W. Berliner made many important contributions to our understanding of the urinary concentrating mechanism. Among these, one must number his demonstration that urine can be rendered hyperosmotic to plasma even when vasopressin is absent, as well as his definition of the role of the glomerular filtration rate (GFR) in the concentrating process [1, 2]—points that had also been suggested by several other investigators [reviewed in 3, 4]. In postulating how urine might be concentrated without vasopressin purely by changes occurring within the kidney [1], Dr. Berliner expressed the essence of a message, which we still tend to overlook today, namely, that “…although it is commonly stated that the function of ADH is to cause the excretion of a hypertonic urine, its more important function might be better defined as preventing the excretion of a dilute urine.”The availability of the Brattleboro rat, which has an inherited deficiency for synthesizing vasopressin [5], made it possible to further explore the mechanisms by which urine can be concentrated in the apparent absence of the hormone. We here review these experiments, paying special attention to the role of GFR in the process

INTERNATIONALIZATION OF UNIVERSITY AND LEARING OF UNIVERSITY AND LEARNING PROCESS: WEB 2.0 DIMENTIONS

Today Web 2.0 means a qualitative leap in computer technologies that have made the internet environment more creative, participative and socializing. Its dimensions are present in almost every aspect and process at a university. This paper gives an insight about usage and possibilities of such dimensions

INTERNATIONALIZATION OF UNIVERSITY AND LEARING OF UNIVERSITY AND LEARNING PROCESS: WEB 2.0 DIMENTIONS

Today Web 2.0 means a qualitative leap in computer technologies that have made the internet environment more creative, participative and socializing. Its dimensions are present in almost every aspect and process at a university. This paper gives an insight about usage and possibilities of such dimensions

Auswirkungen des Markennamenwechsels auf den Markenwert : eine Analyse der Konsequenzen von Markenportfoliokonsolidierungen

Die Strategie des Markennamenwechsels bzw. der Markenumbenennung gewinnt in der Marketing-Praxis zunehmend an Bedeutung, insbesondere vor dem Hintergrund von Markenportfoliobereinigungen. Die wissenschaftliche Forschung hat diesem Phänomen allerdings bisher wenig Beachtung geschenkt. Der vorliegende Beitrag präsentiert Motive der Markenkonsolidierung und identifiziert zwei vorherrschende Strategiealternativen (schlagartiger und schrittweiser Namenswechsel). Es wird untersucht, inwieweit der von den Konsumenten wahrgenommene Wert einer bestehenden Marke auf eine andere Marke übertragen werden kann und inwiefern dies von den zwei postulierten Strategieoptionen abhängt. Hierzu wird ein Hypothesensystem entwickelt und in einer Längsschnittstudie mit einem Strukturgleichungsmodell empirisch überprüft. Die Ergebnisse zeigen, dass der Wechsel des Markennamens eine erhebliche Bedrohung für den Markenwert darstellt

Eine Zwei ist eine Drei ist eine Vier

Die Teilnahme Deutschlands an den großen internationalen Schulleistungsstudien hat den Blick auf die Besonderheiten des deutschen Schulsystems geschärft. Während fast alle Industriestaaten im Sekundarbereich integrierte Gesamtschulen anbieten, erfolgt in Deutschland in der Regel schon nach 4 Jahren Grundschule eine Aufteilung in hierarchisch gegliederte Sekundarstufenarten (nachdem in der Grundschule schon etliche Schüler in Sonderschulen überwiesen wurden). Deshalb stellt sich die Frage: Wird die Grundschulempfehlung ihrer Aufgabe, Schüler und Schülerinnen einer Schulart zuzuweisen, gerecht? (DIPF/Orig.