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  • 1
    ISSN: 1432-1912
    Keywords: Key words Vascular permeability ; Vascular endothelial ; growth factor ; Nitric oxide ; Prostaglandin ; Receptor ; tyrosine kinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We investigated role of nitric oxide (NO), prostaglandins (PG) and tyrosine kinase in vascular endothelial growth factor (VEGF)-induced increase in vascular permeability in mouse skin. Subcutaneous injection of VEGF (0.5–2.0 ng/site) induced dose- and time-dependent increase in vascular permeability at the injection site determined by a leakage of Pontamine sky blue. VEGF (1 ng/site)-induced dye leakage was partially inhibited by NG-nitro-l-arginine methyl ester (an inhibitor for both constitutive and inducible NO synthase) (5 and 10 mg/kg, i.v.) and by aminoguanidine (a selective inducible NO synthase inhibitor) (5–20 mg/kg, i.v.), but not by an inactive enantiomer, NG-nitro-d-arginine methyl ester (10 mg/kg, i.v.). Pretreatment with an intraperitoneal injection of indomethacin (a nonselective cyclooxygenase inhibitor) (5 mg/kg) or N-(2-cyclohexyloxy-4-nitrophenyl) methanesulphonamide (a cyclooxygenase-2 selective inhibitor) (1–100 μg/kg) almost completely inhibited the effect of VEGF (1 ng/site). Coadministration of PGE2 (3 and 30 nmol/site) with VEGF did not restore the inhibitory effect of indomethacin on VEGF (1 ng/site)-induced increase in vascular permeability. Lavendustin A (a selective tyrosine kinase inhibitor) (10 and 50 μg/kg, s.c.) dose-relatedly inhibited the VEGF (1 ng/site)-induced increase in dye leakage, whereas its negative control, lavendustin B (10 μg/kg, s.c.) had no effect. Another tyrosine kinase inhibitor, genistein (2.5 mg/kg, s.c.) also inhibited the response. Cycloheximide (a protein biosynthesis inhibitor) (35 mg/kg, s.c.) suppressed the response of VEGF (1 ng/site). Histologically, no cellular infiltration was observed in the area of VEGF injection. These results suggest that increased vascular permeability induced by VEGF is mediated by local production of NO and arachidonic acid metabolites other than PGE2, which are most probably produced by inducible NO synthase and cyclooxygenase-2, respectively. Protein tyrosine kinase-mediated phosphorylation and synthesis of any new proteins are likely to be required in this effect of VEGF in mouse skin.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1619-0904
    Keywords: Tissue engineering ; Bioprosthesis ; Biomaterial ; Cardiovascular surgery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Various vascular and valvlular grafts are commonly used in the treatment of cardiovascular disease. Current prosthetic or bioprosthetic materials lack growth potential, and therefore, subsequent replacement further defeats the concept of primary repair early in pediatric cardiac patients. Tissue engineering is a new discipline that offers the potential to create replacement structures from autologous cells and biodegradable polymer scaffolds. Because tissue-engineering constructs contain living cells, they may have the potential for growth, self-repair, and self-remodeling. Cardiac valve leaflets and large conduits in the pulmonary ciruulation have been made with this tissue-engineering approach in lambs. Venous conduits were also created in dogs. Mixed cell populations of endothelial cells and fibroblasts were isolated from explanted peripheral arteries or vein. A synthetic biodegradable scaffold con-sisting of polyglactin and polyglycolic acid fibers was seeded in vitro with mixed cultured cells. After one week, these autologous cell/polymer constructs were reimplanted in animals. Each animal was then followed periodically by echocardiography and angiography. The animals were sacrificed, and the implanted tissues were examined histologically, biochemically, and biomechanically. A 4-hydroxyproline assay was performed to evaluate the collagen content. The implanted conduit diameters increased as the animals grew during the study period. Histologically, the biodegradable polymer scaffold was completely degraded. Collagen analysis of the constructs showed the development of an extracellular matrix. Immunohistochemical staining demonstrated elastin fiber in the matrix and factor VIII on the inner surface of the conduits. In conclusion, a tissue-engineering approach to constructing cardiovascular structures is feasible using cells of either arterial or venous origin. In these tissue-engineered autografts, transplanted autologous cells generated the proper matrix over the polymer scaffold under physiologic conditions.
    Type of Medium: Electronic Resource
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