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Koleksiyon [17]
Tam Metin [2]
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Dergi Adı [11]
The effects of boric acid-induced oxidative stress on antioxidant enzymes and survivorship in Galleria mellonella

Hyršl, Pavel | Büyükgüzel, Ender | Büyükgüzel, Kemal

Article | 2007 | Archives of Insect Biochemistry and Physiology66 ( 1 ) , pp.23 - 31

Larvae of the wax moth, Galleria mellonella (L.), were reared from first instar on a diet supplemented with 156, 620, 1,250, or 2,500 ppm boric acid (BA). The content of malondialdehyde (MDA, an oxidative stress indicator), and activities of the antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), and glutathione peroxidase (GPx)] were determined in the fat body and hemolymph in the 7th instar larvae and newly emerged pupae. Relative to control larvae, MDA was significantly increased in larval hemolymph, larval and pupal fat body, but decreased in the pupal hemolymph. Insects reared on di . . .ets with 156-and 620-ppm BA doses yielded increased SOD activity but 1,250- and 2,500-ppm doses resulted in decreased SOD activity in larval hemolymph. SOD activity was significantly increased but CAT was decreased in the larval fat body. High dietary BA treatments led to significantly decreased GST activity. However, they increased GPx activity in larval hemolymph. Dietary BA also affected larval survival. The 1,250- and 2,500-ppm concentrations led to significantly increased larval and pupal mortality and prolonged development. In contrast, the lowest BA concentration increased longevity and shortened development. We infer that BA toxicity is related, at least in part, to oxidative stress management. © 2007 Wiley-Liss, Inc Daha fazlası Daha az

Increased diversification of polyhydroxyalkanoates by modification reactions for industrial and medical applications

Hazer, Baki | Steinbüchel, Alexander

Article | 2007 | Applied Microbiology and Biotechnology74 ( 1 ) , pp.1 - 12

A wide range of diverse polyhydroxyalkanoates, PHAs, is currently available due to the low substrate specificity of PHA synthases and subsequent modifications by chemical reactions. These polymers are promising materials for a number of different applications due to their biocompatibility and biodegradability. This review summarizes the large variability of PHAs regarding chemical structure and material properties that can be currently produced. In the first part, in vivo and in vitro biosynthesis processes for production of a large variety of different PHAs will be summarized with regard to obtaining saturated and unsaturated copol . . .yesters and side chain functionalized polyesters, including brominated, hydroxylated, methyl-branched polyesters, and phenyl derivatives of polyesters. In the second part, established chemical modifications of PHAs will be summarized as that by means of grafting reactions and graft/block copolymerizations, as well as by chlorination, cross-linking, epoxidation, hydroxylation, and carboxylation, reactions yield further functionalized PHAs. © 2006 Springer-Verlag Daha fazlası Daha az

Polymeric linoleic acid-polyolefin conjugates: Cell adhesion and biocompatibility

Çakmaklı, Birten | Hazer, Baki | Tekin, İshak Özel | Açıkgöz, Şerefden | Can, Murat

Article | 2007 | JAOCS, Journal of the American Oil Chemists' Society84 ( 1 ) , pp.73 - 81

To diversify edible-oil polymer composite, polymeric linoleic acid (PLina) peroxide was obtained by the auto-oxidation of linoleic acid in a simple way for use as a macroinitiator in free radical polymerization of vinyl monomers. Peroxidation, epoxidation, and/or perepoxidation reactions of linoleic acid under air at room temperature resulted in PLina, having soluble fraction more than 91 weight percent (wt%), with molecular weight ranging from 1,644 to 2,763 Da, and containing up to 1.0 wt% of peroxide. PLina initiated the free radical polymerization of ether styrene (S), methyl methacrylate (MMA), or n-butyl methacrylate (nBMA) to . . . give PLina-g-polystyrene (PS), PLina-g-poly-MMA (PMMA), and PLina-g-poly- nBMA (PnBMA) graft copolymers. The polymers obtained were characterized by proton nuclear magnetic resonance (1H NMR), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC) techniques. Microstructure of the graft copolymers was observed by using scanning electron microscope (SEM). Graft copolymers obtained contained polymeric linoleic acid in a range between 8.5 and 19.3 mol percent (mol%). PLina-g-PS, PLina-g-PMMA and PLina-g-PnBMA graft copolymer samples were also used in cell culture studies. Fibroblast and macrophage cells were strongly adhered and spread on the copolymer film surfaces. These newly synthesized copolymers were tested for their effects on human blood protein adsorption compared with PMMA graft copolymers containing polymeric soybean oil and polymeric linseed oil; interestingly we observed a dramatic decrease in the protein adsorption on the linoleic acid graft copolymer, which is important in tissue engineering. © AOCS 2007 Daha fazlası Daha az

Synthesis and properties of chitosan-modified poly(vinyl butyrate)

Akgün, Sibel | Ekici, Gülsüm | Mutlu, Nilüfer | Beşirli, Necati | Hazer, Baki

Article | 2007 | Journal of Polymer Research14 ( 3 ) , pp.215 - 221

Modification of chitosan by grafting of vinyl butyrate was carried out in homogeneous phase using potassium persulfate as redox initator and 1.5% acetic acid as solvent. The percent grafting and grafting efficiency were analysed and the high grafting efficiency up to 94% was observed. The effects of reaction variables such as monomer concentration, initiator concentration, temperature and reaction time were investigated. It was observed that the solubility of chitosan was markedly reduced after grafting with vinyl butyrate. The grafted product is insoluble in common organic solvents as well in dilute organic and inorganic acids. Cha . . .racterization of the graft copolymers were carried out by using Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM) technics. Characteristic signal of carbonyl group was observed at 1,731 cm-1 which belongs to the poly vinyl butyrate segments in the graft copolymer. The melting transition of the chitosan main chain in the copolymer shifted to 124°C from its original value 101°C. In addition to these, we have also studied topology of the graft copolymer and the SEM micrograph showed continuous homogenous matrix which means there is no phase separation. © Springer Science+Business Media B.V. 2007 Daha fazlası Daha az

Eicosanoids mediate Galleria mellonella cellular immune response to viral infection

Büyükgüzel, Ender | Tunaz , Hasan | Stanley, David | Büyükgüzel, Kemal

Article | 2007 | Journal of Insect Physiology53 ( 1 ) , pp.99 - 105

Nodulation is the predominant insect cellular immune response to bacterial and fungal infections and it can also be induced by some viral infections. Treating seventh instar larvae of greater wax moth Galleria mellonella with Bovine herpes simplex virus-1 (BHSV-1) induced nodulation reactions in a dose-dependent manner. Because eicosanoids mediate nodulation reactions to bacterial and fungal infection, we hypothesized that eicosanoids also mediate nodulation reactions to viral challenge. To test this idea, we injected G. mellonella larvae with indomethacin, a nonsteroidal anti-inflammatory drug immediately prior to intrahemocoelic i . . .njection of BHSV-1. Relative to vehicle-treated controls, indomethacin-treated larvae produced significantly reduced numbers of nodules following viral infection (down from approximately 190 nodules/larva to Daha fazlası Daha az

Penicillin-induced oxidative stress: Effects on antioxidative response of midgut tissues in instars of Galleria mellonella

Büyükgüzel, Ender | Kalender, Yusuf

Article | 2007 | Journal of Economic Entomology100 ( 5 ) , pp.1533 - 1541

Penicillin and other antibiotics are routinely incorporated in insect culture media. Although culturing insects in the presence of antibiotics is a decades-old practice, antibiotics can exert deleterious influences on insects. In this article, we test the hypothesis that one of the effects of dietary penicillin is to increase oxidative stress on insects. The effects of penicillin on midgut concentrations of the oxidative stress indicator malondialdehyde (MDA) and on midgut antioxidant enzyme (superoxide dismutase [SOD], catalase [CAT], glutathione S-transferase [GST], and glutathione peroxidase [GPx]) and transaminases (alanine amin . . .otransferase and aspartate aminotransferase) activities in greater wax moth, Galleria mellonella (L.), were investigated. The insects were reared from first instars on artificial diets containing 0.001, 0.01, 0.1, or 1.0 g penicillin per 100 g of diets. MDA content was significantly increased in the midgut tissues of each larval instar reared in the presence of high penicillin concentrations. Activities of antioxidant and transaminase enzymes did not show a consistent pattern with respect to penicillin concentrations in diet or age of larvae. Despite the increased penicillin-induced oxidative stress in gut tissue, antioxidant and transaminase enzymes did not correlate with oxidative stress level or between each other in larvae of other age stages except for the seventh instar. We found a significant negative correlation of MDA content with SOD and GST activities in seventh instars. SOD activity was also negatively correlated with CAT activity in seventh instars. These results suggest that exposure to dietary penicillin resulted in impaired enzymatic antioxidant defense capacity and metabolic functions in wax moth larval midgut tissues and that the resulting oxidative stress impacts midgut digestive physiology. © 2007 Entomological Society of America Daha fazlası Daha az

Bucklandiella microcarpa (Hedw.) Bednarek-Ochyra & Ochyra (Grimmiaceae, Bryopsida), new to the moss flora of Turkey and South-West Asia

Abay, Gökhan | Uyar, Güray | Çetin, Barbaros | Keçeli, Tamer

Article | 2007 | Cryptogamie, Bryologie28 ( 2 ) , pp.145 - 148

Bucklandiella microcarpa (Hedw.) Bednarek-Ochyra & Ochyra (Racomitrioideae, Grimmiaceae, Bryopsida) is recorded for the first time in Turkey. The specimens were collected from Kaçkar Mountains National Park in Rize province. The nearest localities of this species are in south Carpathians and Ural mountains. Therefore, this new record contributes to a remarkable range extension of this species towards south-west Asia. © 2007 Adac.

Grafting of poly(3-hydroxyalkanoate) and linoleic acid onto chitosan

Arslan, Hülya | Hazer, Baki | Yoon, Sung C.

Article | 2007 | Journal of Applied Polymer Science103 ( 1 ) , pp.81 - 89

Poly(3-hydroxy octanoate) (PHO), poly(3-hydroxy butyrate-co-3- hydroxyvalerate) (PHBV), and linoleic acid were grafted onto chitosan via condensation reactions between carboxylic acids and amine groups, Unreacted PHAs and linoleic acid were eliminated via chloroform extraction and for elimination of unreacted chitosan were used 2 wt % of HOAc solution. The pure chitosan graft copolymers were isolated and then characterized by FTIR, 13C-NMR (in solid state), DSC, and TGA. Microbial polyester percentage grafted onto chitosan backbone was varying from 7 to 52 wt % as a function of molecular weight of PHAs, namely as a function of steri . . .c effect. Solubility tests were also performed. Graft copolymers were soluble, partially soluble or insoluble in 2 wt % of HOAc depending on the amount of free primary amine groups on chitosan backbone or degree of grafting percent. Thermal analysis of PHO-g-Chitosan graft copolymers indicated that the plastizer effect of PHO by means that they showed melting transitions Tms at 80, 100, and 113°C or a broad Tms between 60.5-124.5°C and 75-125°C while pure chitosan showed a sharp Tm at 123°C. In comparison of the solubility and thermal properties of graft copolymers, linoleic acid derivatives of chitosan were used. Thus, the grafting of poly(3-hydroxyalkanoate) and linoleic acid onto chitosan decrease the thermal stability of chitosan backbone. © 2006 Wiley Periodicals, Inc Daha fazlası Daha az

Grafting on polybutadiene with polytetrahydrofuran macroperoxyinitiators. Postpolymerization studies

Macit, Hülya | Hazer, Baki

Article | 2007 | European Polymer Journal43 ( 9 ) , pp.3865 - 3872

Grafting reactions of polybutadiene with macro peroxy initiators and postpolymerization were studied. The cationic polymerization of tetrahydrofuran (THF) initiated by the cationic species derived from bis-(4-bromomethylbenzoyl) peroxide (BBP) or bis-(3,5-dibromomethylbenzoyl) peroxide (BDBP) gave the PTHF macroperoxy initiator (MPI). PTHF-b-PMMA macroperoxy initiator (MPIb) was also obtained by the redox polymerization of methyl methacrylate initiated with the hydroxyl ends of PTHF and Ce(IV) salts without decomposing the peroxide groups in the middle. Macroperoxy initiators thermally grafted on cis-polybutadiene (PBD) with thermal . . . curing to yield graft copolymers containing crosslinked and soluble parts, which were separated by the sol-gel analysis. FTIR spectra of the crosslinked samples indicated the characteristic signals of the PTHF, PBD and PMMA blocks. The crosslinked copolymers decomposed at around 470 °C. Postpolymerization of the crosslinked products indicated the increase in crosslinking density which has been followed by measuring the gradual increase of swelling values. Postpolymerization crosslinking was estimated as a first order reaction rate. © 2007 Elsevier Ltd. All rights reserved Daha fazlası Daha az

Mosses as indicators of atmospheric heavy metal deposition around a coal-fired power plant in Turkey

Uyar, Güray | Ören, Muhammet | Yıldırım, Yılmaz | İnce, Mahir

Article | 2007 | Fresenius Environmental Bulletin16 ( 2 ) , pp.182 - 192

This study was carried out from May 2003 to October 2004 in the vicinity of Çatalagzi coal-fired power plant (CATES) located in Zonguldak, North-West Turkey, in order to investigate atmospheric heavy metal depositions by sampling and analysing Pleurocarp mosses as biomonitoring plants. Initially, ISC-ST (Industrial Source Complex-Short Term) dispersion models were used to determine theoretically the most polluted sites of CATES. After the modelling, sampling was performed in these theoretically determined grids. Samples were analyzed using graphite-furnace atomic absorption spectrometry (AAS) after wet digestion. In the region, the . . .general order of heavy metal content in samples of mosses was determined to be as follows: Fe>Pb>Ni>Cr>Cu>Co>As. Background mean levels of the metals studied, except Cu, were determined and found to be higher than that of European background. The results are also presented in the form of thematic maps using the Geographic Information System (GIS). © by PSP 2007 Daha fazlası Daha az

PMMA-multigraft copolymers derived from linseed oil, soybean oil, and linoleic acid: Protein adsorption and bacterial adherence

Çakmaklı, Birten | Hazer, Baki | Açıkgöz, Şerefden | Can, Murat | Cömert, Füsun B.

Article | 2007 | Journal of Applied Polymer Science105 ( 6 ) , pp.3448 - 3457

Synthesis of Poly(methyl methacrylate), PMMA-multigraft copolymers derived from linseed oil, soybean oil, and linoleic acid PMMA-g-polymeric oil/oily acid-g-poly(3-hydroxy alkanoate) (PHA), and their protein adsorption and bacterial adherence have been described. Polymeric oil/oily acid peroxides [polymeric soybean oil peroxide (PSB), polymeric linseed oil peroxide (PLO), and polymeric linoleic acid peroxide (PLina)] initiated the copolymerization of MMA and unsaturated PHA-soya to yield PMMA-PLO-PHA, PMMA-PSB-PHA, and PMMA-PLina-PHA multigraft copolymers. PMMA-PLina-PHA multigraft copolymers were completely soluble while PMMA-PSB-P . . .HA and PMMA-PLO-PHA multigraft copolymers were partially crosslinked. Crosslinked parts of the PLO- and PSB-multigraft copolymers were isolated by the sol gel analysis and characterized by swelling measurements in CHCl3. Soluble part of the PLO- and PSB-multigraft copolymers and completely soluble PLina-multigraft copolymers were obtained and characterized by spectroscopic, thermal, gel permeation chromatography (GPC), and scanning electron microscopy (SEM) techniques. In the mechanical properties of the PHA-PLina-PMMA, the elongation at break is reduced up to ~ 9%, more or less preserving the high stress values at its break point (48%) when compared to PLina-g-PMMA. The solvent casting film surfaces were studied by means of adsorption of blood proteins and bacterial adhesion. Insertion of the PHA into the multigraft copolymers caused the dramatic increase in bacterial adhesion on the polymer surfaces. PHA insertion into the graft copolymers also increased the protein adsorption. © 2007 Wiley Periodicals. Inc Daha fazlası Daha az

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