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Study of adipokinetic hormone role in insects stressed by entomopathogenic nematodes
IBRAHIM, Emad Ahmed Sayed
In this thesis, the effect of infection elicited by entomopathogenic nematodes (EPNs) Steinernema carpocapsae on Pyrrhocoris apterus and Drosophila melanogaster models were evaluated, and a role of adipokinetic hormones (AKHs) during the infection was characterized. These were monitored by determination of mortality, and various biochemical and physiological characteristics such as AKH levels both in the central nervous system (CNS) and in hemolymph, AKH gene expression in CNS, level of anti-oxidative stress markers, general metabolism and level of nutrients in normal and genetically modified insects. At P. apterus the mortality tests revealed that application of AKH increases the efficacy of EPN treatment. This result was confirmed using the firebugs with AKH receptor deficiency. Further, the increase of AKH expression and AKH levels in CNS and hemolymph seemed to be coordinated after the nematode treatment. At the D. melanogaster model also, the effect of adenosine into the above-mentioned characteristics was included. For this, mutants in AKH (AHK1), adenosine receptor (AdoR1) genes, and in both these genes together (AHK1 AdoR1 double mutant) were employed. Altogether, the results confirmed the involvement of AKH, and partially also adenosine into the antistress defense reactions elicited by the nematobacterial infection. Finally, the last part of the study was focused on examination of the vitellogenin (Vg) role in the defense reaction in firebug body P. apterus affected by two entomopathogenic organisms, the nematode S. carpocapsae and the fungus Isaria fumosorosea. The results revealed that Vg proteins play an important role in the defense against both types of the infections and are also able to kill entomopathogenic bacteria Xenorhabdus nematophila, that are symbionts of S. carpocapsae and that increase toxicity of this nematode.
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Adipokinetic hormone activities in insect body infected by entomopathogenic nematode
IBRAHIM, Emad Ahmed Sayed
The role of adipokinetic hormone (AKH) in the firebug Pyrrhocoris apterus adults infected by the entomopathogenic nematode (EPN) Steinernema carpocapsae was examined in this study. It was found that co-application of EPN and AKH enhanced firebug mortality about 2.5 times within 24 h (from 20 to 51% in EPN vs. EPN + AKH treatments), and resulted in metabolism intensification, as carbon dioxide production in firebugs increased about 2.1 and 1.6 times compared to control- and EPN-treated insects, respectively. Accordingly, firebugs with reduced expression of AKH receptors showed a significantly lower mortality (by 1.6 to 2.9-folds), and lower general metabolism after EPN + AKH treatments. In addition, EPN application increased Akh gene expression in the corpora cardiaca (1.6 times), AKH level in the corpora cardiaca (1.3 times) and haemolymph (1.7 times), and lipid and carbohydrate amounts in the haemolymph. Thus, the outcomes of the present study demonstrate involvement of AKH into the antistress reaction elicited by the nematobacterial infection. The exact mechanism by which AKH acts is unknown, but results suggested that the increase of metabolism and nutrient amounts in haemolymph might play a role.
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Three essays on the inflation targeting regime in Egypt
Ibrahim, Ibrahim Lofti Awad ; Šmídková, Kateřina (vedoucí práce) ; Holub, Tomáš (oponent) ; Cahlík, Tomáš (oponent)
Disertace se skládá ze tří esejí o cílování inflace v Egyptě. Zaměřuje se na otázky: (i) Může centrální banka v Egyptě dosáhnout cenové stability stávajícím režimem? (ii) Je centrální banka nezávislá de facto? (iii) Udržuje centrální banka implicitní cíl pro kurz? Vykonává centrální banka nezávislou měnovou politiku a které proměnné mají prioritu v reakční funkci centrální banky? Do jaké míry může zahraniční šok vysvětlit chování reálného HDP a cenové hladiny ve srovnání s domácím šokem? A které kanály měnové transmise hrají dominantní roli v egyptské ekonomice? Hlavní závěry jsou následující: (i) Poptávka po penězích ani velocita nejsou v Egyptě stabilní. Proto není možné dosáhnout cenové stability ve stávajícím měnovém režimu. (ii) Nezávislost centrální banky udělená stávajícím zákonem není nezávislost de facto. (iii) Odhadnutím strukturálního modelu VAR lze učinit následující závěry ohledně měnové transmise: (1) Centrální banka udržuje implicitní cíl pro kurz. (2) Centrální banka nevykonává nezávislou měnovou politiku. (3) Federální úroková míra a kurz hrají dominantní roli mezi proměnnými důležitými pro měnovou transmisi. (4) Zahraniční šoky jsou důležité pro vysvětlení chování HDP, zatímco domácí šoky vysvětlují lépe chování inflace. (5) Úrokový kanál patří k nejdůležitějším kanálům měnové transmise.
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