Elevated levels of plasma LDL have been correlated with morphological endothelial damages, e.g. reduced antithrombogenity of endothelial cells. Numerical and functional defects of endothelial cells probably influence the necessary separation of blood fractions from subendothelial tissues in a negative sense. In order to describe an imaginable endothelial dysfunction with respect to LDL transport we examined human umbilical venous endothelial cells (HUVEC) in culture under physiological flow conditions. HUVEC in culture after incubation with a LDL concentration of 100 micrograms/ml medium were exposed to defined levels of physiological shear stress, fixed with formalin and stained with oil-red-O. After documentation of oil-red-O staining with a photomicroscope, the amount of stain has been characterized semiquantitatively with the help of an image-analysis system (IBAS II/Zeiss). HUVEC not exposed to shear stress only showed a marginal oil-red-O staining at the cell surface. If they were exposed to shear stress of 0.5 dyn/cm2 they showed in orthogonal view an average increase of 1.3%, in cross-sectional view an average increase of 0.3%. HUVEC exposed to shear stress of 2.5 dyn/cm2 showed in orthogonal view an average increase of 4.6%, in cross-sectional view an average increase of 8.7%.

Erhöhte plasmatische LDL-Konzentrationen sind korreliert mit morphologisch faßbaren Endothelschäden, z.B. mit verminderter Anti-thrombogenität der Endothelzellen. Numerische und funktionelle Endotheldefekte können wahrscheinlich die erforderliche Trennung zwischen Blutbestandteilen und subendothelialen Gefäßwandstrukturen beeinträchtigen. Um eine denkbare Dysfunktion des Endothels in bezug auf den LDL-Transport erfassen zu können, haben wir diesen zunächst unter physiologischen Scherbedingungen in Kulturen humaner Endothelzellen untersucht. Die Endothelzellkulturen sind mit einer LDL-Konzentration von 100 µg/ml Medium inkubiert, mit definierter physiologischer Scherspannung belastet, fixiert und mit Öl-Rot-O gefärbt worden. Die Öl-Rot-O-Färbung ist mikrofotografisch in Aufsicht und Querschnitt dokumentiert und mit Hilfe eines Bild-analysesystems (IBAS Π/Zeiss) semiquantitativ charakterisiert worden. Ungescherte hochkonfluente Endothelzellkulturen zeigen bei physiologischen LDL-Konzentrationen nur eine geringe Öl-Rot-O-Färbung an der Zelloberfläche. Mit 0,5 dyn/cm2 gescherte, hochkonfluente Endothelzellkulturen zeigen durchschnittlich in der Aufsicht eine Zunahme der Öl-Rot-O-Färbung um ca. 1,3%, im Querschnitt eine Zunahme um ca. 0,3%. Mit 2,5 dyn/cm2 gescherte hochkonfluente Endothelzellkulturen zeigen durchschnittlich in der Aufsicht eine Zunahme von ca. 4,6%, im Querschnitt eine Zunahme um ca. 8,7%.

Human umbilical veinous endothelial cells are cultured on artificial substrates precoated with extracellular matrix from bovine corneal endothelial cells. These cultural conditions help cells to keep an elevated maintenance level for otherwise unusual time intervals. Integrity of endothelial cell layers is of special interest for nondisturbed blood circulation. Therefore we look after mechanisms of cell--cell and cell--substrate--adherence. Here we focus on stress fibres, microfilaments, which seem to play an important part in cellular adherence phenomena. Since endothelial cells in vivo are constantly shear stressed by the blood stream we investigated cell--substrate interactions in vitro under dynamical conditions with the help of a modified cone--plate rheometer originally designed for hemorheology. It can be demonstrated in these shearing experiments that toxical substances influence the organization of stress fibres.

In vivo fibrinogen, fibrin and the degradation products may play an important role for example in peritonitis and in ARDS. Formation of edema and of fibrosis might be due to the effects of these substances. In co-cultures of human endothelial cells and fibrocytes/fibroblasts we want to elucidate the role of fibrinogen, fibrin and the degradation products under wound healing conditions. It turns out that these substances may influence proliferation of cells in co-culture adversely in a dose-dependent manner.

Als Modell für eine Wundsituation kann man die Implantation einer Kunststoffgefäß- prothese betrachten. Ein geschlossener Anteil des Körpers — in diesem Falle ein Gefäß — wird aufgetrennt und zwischen den Wundrändern ein Fremdkörper einge- fügt. Vom durchströmenden Blut und von den Wundrändern her tritt nun der Körper in Interaktion mit diesem Fremdkörper. Diese Interaktion zwischen Körper und Fremdkörper umschreibt man mit dem Begriff der Organisationsreaktion. Von den Wundrändern her wird der Fremdkörper langsam allseitig in körpereigenes Gewebe eingehüllt.

The SER allows the "deformability" of individual red blood cells to be quantitated by determining their passage time through a pore (d = 5.8 microns, 1 = 50 microns) under the shear stresses of 1.5 Pa-4 Pa. Using this system, we examined the influence of: 1. cytoplasmic viscosity, 2. membrane viscoelastic properties, 3. area to volume relationship. To change these determinants of RBC-deformability, the cells have been altered with 1. Acetylphenylhydrazine (0.016 mol/l), 2. diamide (0.5 mmol/l), 3. osmotic swelling (200 mosm/l) and osmotic shrinking (480 mosm/l) by suspending the cells in hypo- and hypertonic saline. The passage time has been found to be primarily influenced by changes in cytoplasmic viscosity. The same cells when tested in 4 other systems considered to measure RBC-deformability (filtrometer, packed cell viscometry, rheoscope and ektacytometry) behaved differently.

For the determination of the ability of erythrocytes to deform but not to flow in the microcirculation, the method proposed primarily by Braasch [1] was essentially improved. A measuring device was constructed with which it is possible to produce a histogram of the passage times of a population of erythrocytes through a narrow pore in a membrane. With this apparatus we are able to quantify even discreet changes of the deformability. With this method, we measured the pore passage time of normal red blood cells and cells which are treated with Ca++. A part of the erythrocytes damaged through Ca++ were treated with pentoxifylline to quantify the improvement of deformability. For comparing with the data cited above, the deformability of patients with acute cerebral insult was determined.