Impact of two insect growth regulators on the enhancement of oxidative stress and antioxidant efficiency of the cotton leaf worm, Spodoptera littoralis (Biosd.

This study was conducted to investigate the biochemical defensive mechanisms in larvae of S. littoralis (Biosd.) (Lepidoptera: Noctuidae) collected from cotton fields in two Egyptian Governorates (Kalyobia and Behira), sprayed with spinetoram as well as its impact effect upon carbohydrate metabolism. The role played of spinetoram on different major defensive enzymes like glutathione S-transferases (GSTs) , non specific esterases and acetylcholinesterase(AChE) was discussed. It seems that these enzymes are not greatly involved in the detoxifying process of spinetoram except a marked over production of AChE reached up to 18.7% as well as the concentration of its substrate, ACh with an increase reached up to 42.8%. Spinetoram had also a prominent effect upon carbohydrate metabolism as in glycogen content which was decreased by 34.9%, LDH also was inhibited to 55.7% while trehalase had an elevated activity by 22.8%.In general, Behira Governorate was more affected and more sensitive to spinetoram rather than Kalyobia Governorate. The present work is an introductory study to understand the outline of the mechanism of this bioinsecticide as well as the resistance mechanisms may arise in the future.

A study was conducted to offer a preliminary understanding of the role played by intensively used field controlling agents, two mineral oils, namely Alboleum and Super Misrona oils as well as an IGR, Admiral (pyriproxyfen) with the recommended doses upon adult female mealybug Ferrisia virgata (Pseudococcidae: Homoptera) as an arbitrary model for mealybugs. The present work points out to the importance of the delayed effect of these different compounds. The highest increase in the total protein content was achieved by Admiral reached 29.2% while Super Misrona caused the greatest enhancement in the total carbohydrates concentration (72.93%). On the other hand, Alboleum caused a highly significant inhibition in the activity of glutamic oxaloacetic transaminases (GOT) and glutamic pyruvic transaminases (GPT) reached 82.03 and 22.10 %, respectively. These biochemical changes were intensively discussed. Among most of the tested biochemical parameters, Admiral showed the strongest delayed effect.

http://eajbsa.journals.ekb.eg/ Changes in Antioxidant Enzymes During the Development of the Cotton Leafworm, Spodoptera littoralis (Boisd.

Phenoloxidases (EC.1.14.18.1) are implicated in the immunity of insects toward microorganisms, so oxidative enzymes such as phenoloxidases (PO) from the 7 th instar larvae of the red palm weevil; Rhynchophorus ferrugineus (Oliv.) was partially isolated to characterize its activity using catechol as a substrate. The mitochondrial fraction of larval homogenate was used as enzyme source for partial kinetic studies.Enzyme catalysis was directly proportional to enzyme crude protein conc. up to 200 ug contained in 1 ml of the reaction mixture. Michaelis-Menten kinetics of PO activity was evaluated by constructing Lineweaver Burk double reciprocal plot. Michaelis constant (Km) was, 3.45 X10 -4 M and maximum velocity (V max) of PO reaction was 344.8 O.D.min -1 mg protein -1 . Effect of pH, temperature and substrate concentration on enzyme reaction was tested. Generally, each variable was chosen while other conditions were at optimum found primarily. Reaction rate was optimal at 10 -1 N catechol, neutral medium (pH 7) and 40 C. PO kept its most activity when incubated at 60 C for 15 min before reaction initiation. Phenoloxidases efficiently catalyze catechol. Results in the present study may probably offer a fundamental anchor for future alternative strategies in controlling R. ferrugineus via obstructing its innate defence mechanisms.