Increased expression of platelet-derived growth factor receptor alpha and beta and vascular endothelial growth factor in the skin of patients with chronic venous insufficiency

Growth factors produced by a variety of cells act as signalling peptides through specific cell surface receptor pathways. Functions such as cell proliferation, migration and differentiation have been assigned to each of them. Here, we report alterations of platelet-derived growth factor receptor alpha (PDGFR-alpha) and beta (PDGFR-beta) and vascular endothelial growth factor (VEGF) expression patterns in the progressive clinical stages of chronic venous insufficiency (CVI). A total of 30 punch biopsies were taken from patients with CVI, and VEGF and PDGFR were detected by indirect immunofluorescence and immunoperoxidase techniques. PDGFR-alpha and PDGFR-beta expression was strongly increased in endothelial cells of capillaries, pericapillary cells and connective tissue cells in the stroma of the skin of venous eczema and venous leg ulcer patients, and to a smaller extend in the dermis of those with lipodermatosclerosis. VEGF staining showed a similar expression pattern in the progressive CVI stages. However, staining of vessels in particular might simply reflect binding of VEGF, secreted by keratinocytes or fibroblasts, to its receptors. Growth factor and receptor expression in specimens from telangiectases and reticular veins, and from pigmented areas, resembled that of normal skin. We conclude that PDGFR-alpha, PDGFR-beta and VEGF play an important role in mediating inflammation and epithelial hyperproliferation in venous eczema, inducing connective tissue sclerosis in lipodermatosclerosis, and causing the reduced reepithelialization tendency in venous ulcers. We speculate that endothelial proliferation with chronic venous hypertension might be mediated by these growth factors.     

Position and velocity coupling of postural sway to somatosensory drive

Light touch contact of a fingertip to a stationary surface provides orientation information that enhances control of upright stance. Slight changes in contact force at the fingertip lead to sensory cues about the direction of body sway, allowing attenuation of sway. In the present study, the coupling of postural sway to a moving contact surface was investigated in detail. Head, center of mass, and center of pressure displacement were measured as the contact surface moved rhythmically at 0.1, 0.2, 0.4, 0.6, and 0.8 Hz. Stimulus amplitude decreased with frequency to maintain peak velocity constant across frequency. Head and body sway were highly coherent with contact surface motion at all frequencies except 0.8 Hz, where a drop-off in coherence was observed. Mean frequency of head and body sway matched the driving frequency 相似文献   

A neuron membrane mesh representation for visualization of electrophysiological simulations

We present a process to automatically generate three-dimensional mesh representations of the complex, arborized cell membrane surface of cortical neurons (the principal information processing cells of the brain) from nonuniform morphological measurements. Starting from manually sampled morphological points (3D points and diameters) from neurons in a brain slice preparation, we construct a polygonal mesh representation that realistically represents the continuous membrane surface, closely matching the original experimental data. A mapping between the original morphological points and the newly generated mesh enables simulations of electrophysiolgical activity to be visualized on this new membrane representation. We compare the new mesh representation with the state of the art and present a series of use cases and applications of this technique to visualize simulations of single neurons and networks of multiple neurons.     

The next-generation business meeting: from i-lands to flexible meeting landscapes

Meetings are an important form of interaction in business settings. However, meetings are often not held in a way that makes all participants feel engaged. Meeting support systems try to overcome this obstacle by helping meeting participants in the meeting workflow. This paper takes a complementary approach by distinguishing between different perspectives of good meetings: the peopleware perspective, the generic groupware perspective, and the roomware perspective. It is argued that all these perspectives have to be considered simultaneously when heading toward an ideal meeting system design. The paper presents excerpts of a pattern language that empowers users to improve their meeting. Besides this, the pattern language can be considered as a tool for the designer. After showing, how both groups made use of the patterns, the paper finally presents LivingAgendas, a meeting support system that can accompany the meeting participant through the meeting life cycle.     

Bewertung von Ausfallvarianten für die Netzsicherheitsanalyse

Übersicht Für die On-line-Netzsicherheitsüberwachung wird eine adaptive Güteindex-Prozedur zur dynamischen Erstellung von Ausfallisten vorgestellt. Mit den bisher bekannten Güteindex-Verfahren konnten aufgrund des Verdeckungseffektes meist nicht alle tatsächlich kritischen Varianten als solche erkannt und deklariert werden. In der neuen Prozedur werden die Ergebnisse der Ausfallsimulationsrechnung der unmittelbaren Systemvergangenheit für die Erstellung der aktuellen Ausfalliste verwendet. Mit einer linearen Korrekturfunktion werden dabei die verdeckungseffektbehaftetenG ₂-Werte des Standard-Güteindex-Verfahrens in verbesserte Werte transformiert.

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Contingency assessment for power system security analysis

Contents An adaptive procedure for dynamic contingency selection in the on-line security assessment is proposed. Because of the masking effect in conventional performance index algorithms a possibly large number of critical contingencies is misclassified. In the new procedure results of former security checks are used for evaluating the current contingency list. A linear corrective function is applied to transform the standard second orderG-values into improved values.

     

Crystallization of Fe-Si-B metallic glasses studied by X-ray synchrotron radiation

We have studied the crystallization kinetics of Fe_90-x Si _x B₁₀ amorphous alloys withx ranging from 7 to 21, by synchrotron X-ray radiation. Using energy- dispersive X-ray diffraction, the kinetics of the different crystalline phases evolving during isothermal annealing were followed. These crystalline phases were identified as precipitation of-Fe(Si) and/or Fe₃Si in the amorphous matrix. At a later time or at a higher temperature, Fe₂B starts to crystallize (x < 21 ). Only at low iron concentration (x = 21) was the second phase different, namely Fe₅SiB₂ The hypo- and hyper-eutectic Fe-Si-B glasses were found to crystallize differently. The crystallization processes are discussed in some detail.     

Mechanical aspects of the rare-earth effect

In order to gain a better understanding of the reactive-element effect (REE), the improvement of the oxidation behavior of chromia- or alumina-scale-forming alloys by the addition of small amounts of elements with higher affinity to oxygen than the scale-forming element, it is necessary to clearly distinguish between isothermal oxidation and the behavior of the metal/oxide composite system during cooling. An approach is presented based on fracture-mechanical considerations which correlates critical differential strain between scale and substrate, fracture toughness of the metal/scale interface, scale thickness, defect size and interfacial amplitude. This approach allows a quantitative assessment of the REE for scale adhesion, and although the necessary experimental data are yet lacking, it describes the reported REE in a qualitatively correct manner.     

Combined hydration of tricalcium silicate and β-dicalcium silicate

The mutual interaction of tricalcium silicate (C₃S) and β-dicalcium silicate (β-C₂S) in their combined hydration was studied. The rate of β-C₂S hydration was accelerated significantly in the presence of C₃S. The rate of C₃S hydration was retarded, but only in the presence of large amounts of β-C₂S. The stoichiometric composition and the pore structure of the hydrates formed was altered only unsignificantly when both compound hydrated simultaneously.