Büyükgüzel, Kemal | Tunaz, Hasan | Putnam, Sean M. | Stanley, David

Article | 2002 | Insect Biochemistry and Molecular Biology32 ( 4 ) , pp.435 - 443

We describe prostaglandin (PG) biosynthesis by isolated midgut preparations from tobacco hornworms, Manduca sexta. Microsomal-enriched midgut preparations yielded four PGs, PGA/B2, PGD2, PGE2 and PGF22? all of which were confirmed by analysis on gas chromatography-mass spectrometry (GC-MS). PGA and PGB are double bond isomers which do not resolve on TLC but do resolve by GC; for convenience, we use the single term PGA2 for this product. PGA2 was the major product under most conditions. The midgut preparations were sensitive to reaction conditions, including radioactive substrate, protein concentration (optimal at 1 mg/reaction), rea . . .ction time (optimal at 0.5 min), temperature (optimal at 22°C), buffer pH (highest at pH 6), and the presence of a co-factor cocktail composed of reduced glutathione, hydroquinine and hemoglobin. In vitro PG biosynthesis was inhibited by two cyclooxygenase inhibitors, indomethacin and naproxen. Subcellular localization of PG biosynthetic activity in midgut preparations, determined by ultracentrifugation, revealed the presence of PG biosynthetic activity in the cytosolic and microsomal fractions, although most activity was found in the cytosolic fractions. This is similar to other invertebrates, and different from mammalian preparations, in which the activity is exclusively associated with the microsomal fractions. Midgut preparations from M. sexta pupae, adult cockroach, Periplaneta americana, and corn ear worms, Helicoverpa zea, also produced the same four major PG products. We infer that insect midguts are competent to biosynthesize PGs, and speculate they exert important, albeit unrevealed, actions in midgut physiology. © 2002 Elsevier Science Ltd. All rights reserved Daha fazlası Daha az

Büyükgüzel, Ender | Erdem, meltem | Tunaz, Hasan | Küçük, Ceyhun | Atılgan, Utku Can | Stanley, David | Büyükgüzel, Kemal

Article | 2017 | Comparative Biochemistry and Physiology -Part A : Molecular and Integrative Physiology204 , pp.121 - 128

We posed the hypothesis that inhibition of eicosanoid biosynthesis leads to increased lipid peroxidation in insects. Here we report that rearing the greater wax moth, Galleria mellonella, on media supplemented with selected inhibitors of eicosanoid biosynthesis throughout the larval, pupal and adult life led to major alterations in selected oxidative and antioxidative parameters of wax moth and its ectoparasitoid, Bracon hebetor. The highest dietary dexamethasone (Dex), esculetin (Esc) and phenidone (Phe) led to increased malondialdehyde (MDA) levels and to elevated catalase (CAT) and glutathione-S-transferase (GST) activities in al . . .l developmental stages of host larvae. Dietary Phe resulted in increased MDA levels, and CAT activity in G. mellonella adults by about 4-fold and about 2-fold, respectively. The Phe effect on GST activity in all stages of the wax moth was expressed in a dose-dependent manner, increased to 140 nmol/mg protein/min in larvae. MDA levels were increased by over 30-fold in adult wasps reared on Dex- and Esc-treated hosts. CAT and GST activities were increased in adult parasitoids reared on Esc-and Phe-treated hosts. GST activity of Dex-treated parasitoid larvae increased from about 4 to over 30 nmol/mg protein/min. Dietary Phe led to increased GST activity, by about 25-fold, in adult wasps. These data indicate that chronic inhibition of eicosanoid biosynthesis leads to increased oxidative stress, strongly supporting our hypothesis. The significance of this work lies in understanding the roles of eicosanoids in insect biology. Aside from other well-known eicosanoids actions, we propose that eicosanoids mediate reductions in oxidative stress. © 2016 Elsevier Inc Daha fazlası Daha az

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

Article | 2011 | Journal of Insect Physiology57 ( 4 ) , pp.501 - 507

Eicosanoids are oxygenated metabolites of three C20 polyunsaturated fatty acids, mainly arachidonic acid (AA; 20:4n-6), but also 20:3n-6 and 20:5n-3. Aside from their importance in biomedicine, eicosanoids act in invertebrate biology. Prostaglandins (PGs) influence salt and water transport physiology in insect rectal epithelia and in Malpighian tubules. PGs also influence a few insect behaviors, including releasing oviposition behavior and behavioral fever. Eicosanoids act in ovarian development and in insect immunity. Because eicosanoids act in several areas of insect biology, we posed the hypothesis that chronic inhibition of eico . . .sanoid biosynthesis, in the absence of microbial challenge, can influence insect life table parameters, including developmental time, survival, adult longevity and parasitoid fecundity. Here we report that inhibiting eicosanoid biosynthesis throughout the larval life exerted minor influences on some life table parameters of the greater wax moth, Galleria mellonella and its ectoparasitoid, Bracon hebetor, however, the inhibitors strongly reduced the production and hatchability of the parasitoids' eggs. The significance of the work relates to the potentials of understanding and targeting eicosanoid systems as a platform for developing new technologies of insect pest management. As seen here, the impact of targeting eicosanoid systems is seen in crucial moments of insect life histories, such as reproduction or immune challenge rather than in overall larval development. © 2011 Elsevier Ltd Daha fazlası Daha az

Durmuş, Yonca | Büyükgüzel, Ender | Terzi, Burçin | Tunaz, Hasan | Stanley, David | Büyükgüzel, Kemal

Article | 2008 | Journal of Insect Physiology54 ( 1 ) , pp.17 - 24

Nodulation is the quantitatively predominant insect cellular immune function activated in response to bacterial, fungal and some viral infections. We posed the hypothesis that parasitoid insects express melanotic nodulation reactions to viral challenge and that eicosanoids mediate these reactions. Treating fifth-instar larvae of the ichneumonid endoparasitoid Pimpla turionellae with Bovine Herpes Simplex Virus-1 (BHSV-1) induced nodulation reactions in a challenge dose-dependent manner. Experimental larvae treated with the cyclooxygenase inhibitor, indomethacin, the lipoxygenase inhibitor, esculetin, and the phospholipase A2 inhibit . . .or, dexamethasone, resulted in severely impaired nodulation reactions to our standard BHSV-1 challenge dose. The immunoinhibitory influence of dexamethasone was reversed in larvae reared on culture medium amended with arachidonic acid, the fatty acid precursor of eicosanoid biosynthesis. Larvae that had been reared on media amended with indomethacin, esculetin, or dexamethasone were also compromised in their nodulation reactions to viral challenge. The influence of the orally administered pharmaceutical was expressed in a dose-dependent manner. Finally, wasp larvae reared in the presence of indomethacin and dexamethasone expressed significantly decreased levels of phenoloxidase activity in response to viral challenge. These findings draw attention to the idea that endoparasitoid insects express cellular immune reactions to viral challenge; they also support our hypothesis that eicosanoids mediate nodulation reactions to viral challenge in these highly specialized insects. © 2007 Elsevier Ltd. All rights reserved Daha fazlası Daha az

Büyükgüzel, Ender | Tunaz, Hasan | Büyükgüzel, Kemal

Other | 2006 | Türk Biyokimya Dergisi31 ( 4 ) , pp.194 - 206

Karasal ortamda yaşıyan hayvansal organizmaların koku alma duyuları (olfaktör sistem) uçucu hidrofobik molekülleri tespit ederek seçebilecek şekilde özelleşmiştir. Bu moleküllerin bazıları bitkisel kaynaklı uçucu bileşikler olup bazıları da hayvansal organizmalar tarafından salınan hidrofobik özellikte, hidrokarbon yapısında ve feromonlar olarak isimlendirilen koku molekülleridir. Böceklerin antenlerinin birincil görevi, karşı eşeyden salınan eşey feromonlarını, diğer fizyolojik ve davranışsal işlevleri gerçekleştiren semiokimyasalları ve bitkisel kaynaklı uçucu molekülleri içeren kokuları algılamaktır. Lepidoptera takımına ait güve . . . türlerinin antenlerinde trikoid ve bazikonik olarak isimlendirilen iki olfaktör duyu almacı (sensilyum) belirlenmiştir. Trikoid sensilyumlar feromonları algılamak üzere özelleşmiştir. Hidrofobik semiokimyasallar koku bağlayıcı proteinler tarafından bağlanarak çözünür forma dönüştürüldükten sonra sensillar lenfteki sulu ortamdan sinyal iletiminin başlatıldığı olfaktör reseptöre doğru taşınır. Bu proteinler altı adet sistein amino asidi taşıması nedeniyle benzer yapıda olup feromon bağlayan proteinler ve koku bağlayan proteinler olarak iki alt gruba ayrılır. Üç adet disülfür bağı oluşturan bu sistein amino asitleri proteinlerin üç boyutlu yapılarının kararlılığı için gereklidir. Feromonlar böcekler, diğer hayvan grupları ve insanlar tarafından kimyasal iletişimi sağlamak amacıyla salınan kokusuz, doğal moleküllerdir. Bu moleküller, dişi böceğin erkeğini kilometrelerce uzaktan bulabilmesini sağlayacak kadar etkindir. Feromon bağlayan proteinler Lepidoptera takımına ait güveler ve diğer böcek türlerindeki çeşitli duyu organlarında bulunan, düşük moleküler ağırlığa sahip (13-17 kDa) heliks yapısında proteinlerdir. Koku bağlayan proteinler ise kimyasal duyu sensilyumlarının lenf sıvısında oldukça yoğun olarak bulunan düşük moleküler ağırlıklı (15 kDa) çözünür proteinlerdir. Diğer birçok böcek türlerinin çeşitli duyu organlarında küçük bir protein grubu daha belirlenmiştir. Dört sistein amino asidi içermesinden dolayı feromon bağlayıcı protein ve koku bağlayıcı protein ile amino asit dizilişi bakımından daha az benzerlik gösteren bu proteinler, kimyasal duyu proteinleri olarak ayrı bir gruba dahil edilir. Bunlar koku ve tat gibi kimyasal sinyallerin algılanmasından sorumlu olup çeşitli kimyasalların hava ve su ortamından reseptörlere taşınmasında rol oynar. The olfactory systems of terrestial animals are designed to trap and sample volatile hydrophobic molecules. Some of these molecules are odorants, such as volatile plant compounds and pheromones emitted from the other organisms. Insect antennae have a primary function of detecting odors including sex pheromones and plant volatiles. In moths, the organs devoted to olfactory perception have been identified in antennae as the sensilla trichoid and basiconic, the former being tuned to the perception of pheromones. The hydrophobic semiochemicals are solublized by odorant-binding proteins and transported through an aqueous environment (sensillar lymph) to the olfactory receptors, where the signal transduction starts. These proteins, subdivided into pheromone-binding proteins and general odorant-binding proteins, all have a hallmark of six conserved cysteine residues forming three disulfide bridges which are essential for the rigidity of their three-dimensional structures. Pheromones are naturally occuring odorless chemical messenger compounds found in all insects, animals, and humans. They could attract male insects from a long distance exceeding kilometers. Pheromone-binding proteins are small helical proteins (13-17 kDa) present in several sensory organs from moth and other insect species. Odorant-binding proteins are small (15 kDa) soluble proteins, very concentrated in the lymph of chemosensory sensilla. A third class of small proteins has been identified in several sensorial organs from a number of insect orders. They have been separated into a group of chemosensory proteins, characterized by four cystein residues and with low sequence similarity to odorant-binding proteins. They are involved in chemoperception (olfaction and taste) and to play a role in chemical transport from air or water to chemosensitive receptors Daha fazlası Daha az

Tunaz, Hasan | Park, Youngjin | Büyükgüzel, Kemal | Bedick, Job C. | Aliza, A.R. Nor | Stanley, David W.

Article | 2003 | ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY52 ( 1 ) , pp.1 - 6

Intracellular phospholipase A(2) (PLA(2)) is responsible for releasing arachidonic acid from cellular phospholipids, and is thought to be the first step in eicosanoid biosynthesis. Intracellular PLA(2)s have been characterized in fat body and hemocytes from tobacco hornworms, Manduco sexta. here we show that bacterial challenge stimulated increased PLA(2) activity in isolated hemocyte preparations, relative to control hemocyte preparations that were challenged with water. The increased activity was detected as early as 15 s post-challenge and lasted for at least 1 h. The increased activity depended on a minimum bacterial challenge d . . .ose, and was inhibited in reactions conducted in the presence of oleyoxyethylphosphorylcholine, a site-specific PLA(2) inhibitor. In independent experiments with serum prepared from whole hemolymph, we found no PLA(2) activity was secreted into serum during the first 24 h following bacterial infection. We infer that a hemocytic intracellular PLA(2) activity is increased immediately an infection is detected. The significance of this enzyme lies in its role in launching the biosynthesis of eicosanoids, which mediate cellular immune reactions to bacterial infection Daha fazlası Daha az