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Öğe Caffeic acid phenethyl ester prevents intestinal reperfusion injury in rats(W B Saunders Co-Elsevier Inc, 1999) Koltuksuz, U; Özen, S; Uz, E; Aydinç, M; Karaman, A; Gültek, A; Akyol, ÖBackground/Purpose: Ischemia-reperfusion injury is encountered frequently in conditions that diminish intestinal blood flow. Caffeic acid phenethyl ester (CAPE), which is a specific component of the honeybee hive product propolis, exhibits potential antioxidant: properties. This experimental study was designed to determine the effect of CAFE on ischemia-reperfusion injury in rat intestine. Methods: Fifty rats were divided into 5 groups: sham (SH), saline ischemia (SI), saline reperfusion (SR), CARE ischemia (CI), and CARE reperfusion (CR). Either CAFE, 10 mu mol/kg, or saline was administered intraperitoneally 30 minutes before ischemia. Intestinal ischemia for 30 minutes and reperfusion for 60 minutes were applied. Ileum specimens were obtained to determine the tissue levels of malondialdehyde, superoxide dismutase, catalase, and histological changes. Results Malondialdehyde levels in the CR group did not increase after reperfusion when compared with the CI group. However, statistically significant differences were observed between the SR and SI groups. Additional mucosal injury in the CR group when compared with the CI group was not observed. Whereas, there was a statistically significant increase in mucosal injury in the SR group. Reperfusion did not cause further injuries through both biochemical and histological parameters in the CR group. Conclusions: Results of this study showed that prophylactic administration of CAFE in ischemic condition prevents reperfusion injuries by eliminating oxygen radicals and inhibiting polymorphonuclear leukocyte infiltration. CARE may be useful in combating the diseases of oxidative stress. J Pediatr Surg 34:1458-1462. Copyright (C) 1999 by W.B. Saunders Company.Öğe Effect of caffeic acid phenethyl ester on survival of axial pattern flaps in rats with ischaemia-reperfusion injuries(Taylor & Francis As, 2006) Bilen, BT; Kilinç, H; Alaybeyoglu, N; Çelik, M; Iraz, M; Sezgin, N; Gültek, AOxygen-derived free radicals have been implicated in the pathogenesis of tissue injury after ischaemia-reperfusion. Caffeic acid phenethyl ester ( CAPE), an active ingredient of honeybee propolis, has been identified as having potent antioxidant and anti-inflammatory properties. We evaluated the ability of CAPE applied intraperitoneally in reducing tissue injury after ischaemia-reperfusion. To investigate whether treatment with CAPE modifies the concentrations of the endogenous indices of oxidant stress, we examined its effects on a model of flap ischaemia-reperfusion injury in rats. CAPE (10 mu mol/ kg) was given through the peritoneum before reperfusion. CAPE given intraperitoneally had an inhibitory effect on tissue injury after ischaemia-reperfusion comparable to that of a control group. The anti-inflammatory and antioxidant properties of CAPE may contribute to its suppression of tissue injury.Öğe The grafting of Rhodamine B onto sol-gel derived mesoporous silicas(Elsevier Sci Ltd, 2003) Seçkin, T; Gültek, A; Kartaca, SAmorphous meseporous silica, silica foams and silica nanotubes have been prepared by the controlled hydrolysis of tetraethoxysilane in various environments. A self-similar structure was obtained in all cases. Rhodamine B was post grafted onto the meseporous silica foam which has been modified with gamma-glycidyloxypropyl trimethoxysilane. The grafting and post grafting efficiency of gamma-glycidyloxypropyl trimethoxysilane as well as the post grafting efficiency of Rhodamine B on meseporous silica foam were studied, respectively. Basic physicochemical properties of the modified particles are given. When the hybrid pigments were exposed to UV radiation pulses, the emission of the hybrid pigments was increased. (C) 2002 Elsevier Science Ltd. All rights reserved.Öğe Poly(methacrylic) acid and ?-methacryloxypropyltrimethoxy silane/clay nanocomposites prepared by in-situ polymerization(Tubitak Scientific & Technological Research Council Turkey, 2002) Gültek, A; Seçkin, T; Önal, Y; Içduygu, MGPoly(methacrylic acid) and poly(acrylic acid) nanocomposites were prepared by in-situ polymerization of gamma-methacryloxypropyltrimethoxysilane (A174)/clay nanocomposites in which the macromonomer was generated by grafting A-174 onto activated clay samples via hydroxyl groups or via intercalation. In- situ polymerization was carried out in the presence of an initiator. It was found that the structural affinity between the methacrylic or acrylic acid monomers and the amount of clay played an important role in the hybrid structure. The nanocomposites were quantified by both X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), and differential thermal analysis (DTA).Öğe Polymerization and characterization of acrylonitrile with ?-methacryloxypropyltrimethoxy-silane grafted bentonite clay(Wiley, 2002) Seçkin, T; Gültek, A; Içduygu, MG; Önal, YNovel natural clay-polymer hybrid materials are prepared from natural bentonite that was modified with silane-coupling agent, gamma-methacryloxypropyltrimethoxysilane (A-174), and acrylonitrile. By changing the molar ratio of acrylonitrile in the initial monomer feed, several clay-hybrid materials were prepared. The structure and thermal stability of hybrid materials were investigated by various methods. The A-174-modified bentonite was dispersed in a solution of acrylonitrile in toluene. In this system, radical polymerization in the presence of AIBN was carried out. Product formed at the particle surface was either physically bound by entanglement or chemically bound by covalent bonding to the silane. In this way, core-shell morphology was obtained with an inorganic core and a polymer shell. The results showed that bonding at the surface of bentonite took place by hydrolytic cleavage of methoxy groups of A-174 with hydroxy groups of bentonite. (C) 2002 John Wiley Sons, Inc.Öğe Postgrafting of Congo red dye onto hyperbranched mesoporous silica with terminal amino groups(John Wiley & Sons Inc, 2003) Seçkin, T; Gültek, ACongo red dye has been postgrafted onto mesoporous silica that was prepared by the controlled hydrolysis of tetraethyl orthosilicate in the presence of organic agents. Surface grafting of mesoporous silica having amino groups as initiator sites was prepared from gamma-aminopropyl-trimethoxysilane by sol-gel process. The postgraffing reaction of Congo red onto silica with terminal amino groups was achieved by a repeated step of the addition of methyl acrylate to amine groups followed by the amidation of the resulting ester moieties with ethylene diamine. Postgrafting efficiency of all materials has been outlined. Because postgrafting efficiency values have been found to be smaller than theoretical values, it is concluded that the resulting product was more likely to be a hyperbranched polymer rather than a true dendrimer at higher generations. The postgrafted structures with amino-terminal groups provide an attractive site for binding Congo red dye that not only persists in its characteristic properties, but also has exceptional hybrid properties possessed by mesoporous silica. (C) 2003 Wiley Periodicals, Inc.Öğe Preparation and characterization of polybenzimidazole-clay hybrid materials(Elsevier Science Sa, 2004) Gültek, A; Icduygu, MG; Seçkin, TThermally stable bentonite-polybenzimidazole (PBI) nanocomposites were synthesized from reactive organoclay and polybenzimidazole. The reactive organoclay was formed by using hexadecylpyridinium chloride (CPC) as a swelling agent for silicate layers of bentonite. The swelling process was carried out through ion exchange reaction between the end group of hexadecylpyridinium chloride salt and the sodium ion in bentonite. This irreversible swelling monitored by measuring the cation exchange capacity (CEC) of the bentonite solutions. Dispersion of the modified clay in the polybenzimidazole matrix resulted in nanostructured material containing intercalated polymer between the silicate layers. X-ray and thermal analysis confirmed structure of the now hybrid materials. The glass transition temperature and the thermal decomposition temperatures of this type bentonite-PBI were found to be higher than that of pure PBI. (C) 2003 Elsevier B.V. All rights reserved.
