Protective effect of leptin against ischemia-reperfusion injury in the rat small intestine

BACKGROUND: The small intestine is extremely sensitive to ischemia-reperfusion (I/R) injury and a range of microcirculatory disturbances which contribute to tissue damage. Previous studies have shown that leptin plays an important physiological role in the microvasculature. The aim of this study was to evaluate the protective effects of leptin in I/R – induced mucosal injury in the small intestine. METHODS: Forty rats were divided into 5 groups (n = 8). Group I was subjected to a sham operation. Following mesenteric ischemia in group II (control); physiologic saline 1 cm(3), in group III; leptin 100 μg/kg, and physiologic saline 1 cm(3), in group IV; N(G)-L-arginine methyl ester (L-NAME) 20 mg/kg, and physiologic saline 1 cm(3), in group V; leptin 100 μg/kg, L-NAME 20 mg/kg, and physiologic saline 1 cm(3 )were given intra-peritoneally. In these groups, an I/R procedure was performed by occlusion of the superior mesenteric artery for 45 min followed by 120 min reperfusion. After reperfusion, the small intestines were resected for malondialdehyde (MDA) and nitric oxide (NO) concentration and histopathologic properties. Mucosal lesions were scored between 0 and 5. Tissue MDA and NO concentration and histopathologic grades were compared statistically. RESULTS: Tissue MDA level significantly increased (P < 0.05), tissue NO level significantly decreased in group V animals, compared to group III animals respectively (P < 0.001). Histopathologically, intestinal injury significantly decreased in the leptin treated ischemic group. CONCLUSION: Leptin can be used safely in mesenteric occlusive diseases, since it induces NO formation and release in mesenteric vessels

Nitrosocarbonyl Hetero-Diels–Alder Cycloaddition: A New Tool for Conjugation

It is demonstrated that nitrosocarbonyl hetero-Diels-Alder chemistry is an efficient and versatile reaction that can be applied in macromolecular synthesis. Polyethylene glycol functionalized with a hydroxamic acid moiety undergoes facile coupling with cyclopentadiene-terminated polystyrene, through a copper-catalyzed as well as thermal hetero-Diels-Alder reaction. The mild and orthogonal methods used to carry out this reaction make it an attractive method for the synthesis of block copolymers. The resulting block copolymers were analyzed and characterized using GPC and NMR. The product materials could be subjected to thermal retro [4 + 2] cycloaddition, allowing for the liberation of the individual polymer chains and subsequent recycling of the diene-terminated polymers. © 2014 American Chemical Society

Polypropylene-based graft copolymers via CuAAC click chemistry

Graft copolymers from commercial chlorinated polypropylene (PP-Cl) possessing either poly(ethylene glycol) (PEG) or poly(ε-caprolactone) (PCL) grafts are synthesized by copper (I)-catalyzed azide-alkyne cycloaddition ‘click’ reaction (CuAAC). For this purpose, azido-functional polypropylene is prepared by nucleophilic substitution of chlorine groups of PP-Cl with azidotrimethylsilane-tetrabutylammonium fluoride. Whereas, the clickable alkyne end-functional PEG and PCL are independently synthesized by esterification reaction of poly(ethylene glycol) methyl ether with 4-pentyonic acid at room temperature and ring-opening polymerization of ε-caprolactone using stannous octoate as catalyst and propargyl alcohol as initiator. Finally, the corresponding graft copolymers, PP-g-PEG and PP-g-PCL, with different surface properties were successfully synthesized by CuAAC ‘click’ reaction under mild condition. Spectral, chromatographic and thermal analyses at various stages prove the formation of desired polypropylene-based graft copolymers with well-defined properties. Furthermore, the water contact angle values of PP-Cl, PP-g-PEG and PP-g-PCL are found as 90±1°, 78±1.8° and 83±2.1°, respectively

extracts of Convolvulus species

The use of plants in the treatment of various diseases has a history as old as humanity. Turkey, with its rich flora, is a unique resource for this kind of investigations. Convolvulaceae genus is used for the prevention of various neurodegenerative diseases and intestinal problems in the traditional folk medicine. It is also reported in the scientific literature that these species possess an inhibition potential for the growth of certain tumor cells. In order to evaluate the potential toxic effects of these species, 1% ethanol extracts were administered to experimental groups and the antioxidant enzyme activities aside from the lipid peroxidation levels were determined in the selected organs. In comparison to control group, a decrease in liver catalase (from 10.69 to 8.61, 7.58 and 5.60 U/mg protein for Convolvulus phrygius, Convolvulus aucheri and Convolvulus galaticus, respectively) and glutathione peroxidase (from 2.21 to 2.12, 0.85 and 0.76 U/mg protein for C. phrygius, C. aucheri and C galaticus, respectively) activities were observed in all groups that were fed with ethanol extract (1%) for a period of one month. A decrease in antioxidant enzyme activities along with the increase in lipid peroxidation levels and blood biochemical parameters is a significant marker of liver injury. Similar results were found for the kidney except from the group fed with C phrygius extract. It is obvious that studied concentrations of Convolvulus species inhibits the liver/kidney antioxidant enzymes in vivo and stimulates the loss of membrane function via peroxidation. Since all these fluctuations in antioxidant enzyme activities cause toxicity in the related organs, further investigations are strongly recommended to find the optimum dose and exposure time prior to medical uses of these species. (C) 2015 Elsevier B.V. All rights reserved

Synthesis and characterization of sugar-based methacrylates and their random copolymers by ATRP

Various sugar-based methacrylate monomers have been prepared and randomly copolymerized with methyl methacrylate (MMA) using classical atom transfer radical polymerization (ATRP). Firstly, four different sugar-based methacrylates are synthesized by two-step method: (i) etherification of protected monosaccharides with epichlorohydrin and (ii) following ring-opening reaction of obtained epoxides with methacrylic acid (MAA) in the presence of triethylamine. Next, these monomers are copolymerized with MMA via ATRP at 90 °C to obtain corresponding random copolymers. The molecular weights of the copolymers are determined by both GPC (gel permeation chromatography) and 1H-NMR (nuclear magnetic resonance spectroscopy) analyses and found as 10600~16800 and 12200~18500 g/mol, respectively. Moreover, the copolymer compositions are also determined by 1H-NMR analysis using characteristic signals of the monomers and found as about 94.1~97.8%, which are good agreement with feeding ratio. In addition, the glass transition temperatures of copolymers are found as 101.2~102.9 °C by changing type and composition of sugar-based methacrylate monomers. Overall, a series of well-defined random copolymers comprising different sugar-based methacrylates and methyl methacrylates were successfully synthesized by classical ATRP method