Experimentelle Ermittlung der Ölströmung in tauchgeschmierten Schneckengetrieben

Forschung im Ingenieurwesen - Schneckengetriebe finden sich in verschiedenen Anwendungen als Stell- und Leistungsgetriebe. Aufgrund der Realisierbarkeit einer hohen Übersetzung bei kleinem...     

Interleukin-8 and GRO alpha prime human neutrophils for superoxide anion production and induce up-regulation of N-formyl peptide receptors

Interleukin-8 (IL-8) and GRO alpha are leukocyte-attracting peptides of the chemokine family. To study the priming potential of these chemokines, we measured superoxide anion production and up-regulation of N-formyl peptide receptors in human neutrophils. IL-8 and GRO alpha themselves did not stimulate production of significant amounts of superoxide anions but potentiated N-formyl peptide-induced superoxide anion production in a concentration-dependent manner. Binding measurements by flow cytometry at 37 degrees C with fluorescein-labeled N-formyl peptide revealed enhanced total N-formyl peptide binding after pretreatment of neutrophils with IL-8 and GRO alpha. Binding measurements performed at 4 degrees C indicated that the chemokines stimulated the up-regulation of N-formyl peptide receptors at the cell surface but did not alter their affinity for the ligand. This study indicates that IL-8 and GRO alpha, in addition to their known chemotactic activity, prime neutrophils for superoxide anion production, presumably by up-regulating the number of receptors for strong superoxide-anion-triggering stimuli.     

Persistent inhibition of neutrophil function by glucose based dialysis solutions

Local defense mechanisms play an important role in prevention of peritonitis, a major complication of continuous ambulatory peritoneal dialysis (CAPD) therapy. The authors have shown that hypertonic, lactate containing glucose based dialysis solutions (GBDS) used in CAPD lead to an immediate and complete pH-dependent inhibition of actin polymerization and phagocytosis in polymorphonuclear neutrophils (PMN) in vitro. Earlier studies have shown that the pH of the fluid equilibrates from 5.2 to approximately 6.4 during the first 30 min of intraperitoneal dwell time. Thus, the authors designed the current study to determine whether the inhibition of cytoskeletal function and intracellular acidosis induced by acidic solutions are reversed by this pH adjustment. To this end, actin polymerization, phagocytosis, and intracellular pH were studied in PMN isolated from healthy human donors during a 10 min incubation in commercially available GBDS at pH 5.2 and again after pH adjustment to 6.4. Actin polymerization was assessed by measuring F-actin content using NBD phallacidin staining and fluorescence activated cell scanner analysis. Phagocytosis was assessed using zymosan particles, and intracellular pH was monitored by spectrofluorometry. The impairment of cytoskeletal alterations in cells exposed to GBDS at pH 5.2 was persistent and not fully reversed by adjusting the pH. Likewise, phagocytosis remained markedly inhibited and intracellular pH did not rise after adjustment of pH. Thus, the results demonstrate a persistent cytotoxic effect of CAPD solutions on human phagocytes. The authors think that CAPD solutions must be modified to provide a more physiologic pH environment for proper phagocyte function.     

Comprehensive simulation methods for crossed helical gear sets with the main focus on the calculation of contact patterns

Forschung im Ingenieurwesen - Crossed helical gear sets consist of two helical gears paired at an angle of intersection between Σ > 0° and Σ ≤ 90°...     

Expression and functional activity of the IL-8 receptor type CXCR1 and CXCR2 on human mast cells

To further elucidate mechanisms involved in mast cell accumulation at sites of cutaneous inflammation, we have studied the ability of human leukemic mast cells (HMC-1 cells) to express functionally active IL-8 receptors. Expression of mRNA for both types of IL-8 receptors (CXCR1 and CXCR2) was demonstrated by PCR and of both proteins by flow cytometry. Binding and competition studies with 125I-labeled IL-8 and its homologue melanoma growth stimulating activity (125I-labeled MGSA) revealed two specific binding sites for IL-8, K1 = 1.1 x 10(11) M(-1) and K2 = 5 x 10(7) M(-1); and for MGSA, K1 = 2.8 x 10(10) M(-1) and K2 = 5 x 10(7) M(-1). This finding was supported by a dose-dependent rise of cytosolic free calcium concentration ([Ca2+]i) induced by both chemokines and to a lesser extent by the homologue neutrophil-activating peptide-2 (NAP-2). A significant migratory response of human leukemic mast cells (HMC-1) was observed with all three chemokines at a range from 10(-8) M to 10(-9) M. Moreover, the formation of cellular F-actin was induced in a rapid, dose-dependent fashion, with a maximally 1.7-fold increase at 10(-7) M. Using postembedding immunoelectron microscopy, we could show the expression of CXCRI on the cytoplasmatic membrane of isolated human skin mast cells whereas CXCR2 was located in mast cell-specific granules. These findings demonstrate for the first time the functional expression of both types of IL-8 receptors on human mast cells, suggesting a role for their ligands during mast cell activation and recruitment.