الفهرس 
List of abbreviations
Microbial controlOnly 14 pages are availabe for public view
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Abstract
The medical importance of mosquito attract research groups especially in the field of their control. Control of mosquitoes guarantee the avoidance of spreading the diseases they transmit. The major question while designing to control mosquito larvae was to select between immature or adult stages. Generally, immature stages of mosquito are preferred in management programs as their aquatic habitat allow for restricting the insecticide application area compared to the flying adults. Additionally, the limitation accompanied with using traditional insecticides push toward looking for modern methods to regulate mosquito populations. Nanostructures are now widely used in management of pests worldwide. In the current study, the nanoparticles of zinc oxide (ZnONPs) (10-30 nm) were used against larvae of C. pipens.
The main purposes of the current work can be summarized into three main points representing the practical parts of the dissertation:
1. Determination of the toxic values of ZnONPs against larval C. pipens these values aee detrimental in the applicability of this potential insecticide. Probit analysis was used to determine the toxicity values of ZnONPs. Based on the data generated from this experimental part, the toxicity values are calculated and allowing selection of the appropriate sublethal concentration for morphological, physiological and developmental studies.
2. Following determination of the toxicity, it was needed to analyze the downstream pathways involved in ZnONPs toxicity. To this end, several histological, ultrastructural, biochemical and developmental manipulations were observed or analyzed following NPs treatment. The histological studies were performed on the alimentary canal and Malpighian tubules which are the primary organs interacting with NPs. The ultrastructural studies were classified into morphological (external) studies using SEM or internal studies using TEM. The biochemical studies addressed the changes in the free radicals-antioxidant and detoxifying enzymes balance following treatment with ZnONPs. The developmental studies included mathematic calculation of the larval and pupal period following treatment withmZnONPs.
3. As a toxic pesticide, the effect of NPs on larval mosquitoes induces either acute or chronic effects. A typical insecticide causes chronic effects on the target pest to ensure the highest control rate of the pest. In the current study we designed a series of experiments to analyze such effect. The experiments were built up based on the application of a recovery period in ZnONPs treated larvae to allow the larvae to recover from the inhibitory effects of ZnONPs. To test such factor, larvae were treated with LC30 of ZnONPs for 72h, allowed to recover without medication for additional 72h and the same parameters (histological, ultrastructural, biochemical and developmental) were reanalyzed.
The obtained results can be summarized as follows:
i. ZnONPs induced toxic effects on the second instar of C. pipens larvae. The recorded toxicity values were 2.3 g/L and 0.24g/L for LC50 and LC30, respectively.
ii. Following determination of toxicity values, a sublethal concentration (LC 30) was selected for subsequent experiments and their results revealed :-
a- Morphological abnormalities: Larvae treated with a sublethal concentration LC30 of ZnONPs suffered reduced growth rate, longer developmental period and malformations in the breathing tube as interpreted from microscopic and SEM images or calculated values of mean larval and pupal periods.
b- Histological changes in the form of appeared histopathological signs in treated larvae the treated larvae suffered negative signs on midgut, hindgut and Malpighian tubule epithelia which appeared in the form of columnar cell vaculation and damage of the microvilli.
c- Ultrastructural changes where the treated larvae showed clear abnormal appearance of the gastric caeca and midgut epithelia under transmission electron microscope (TEM). These condensation of the nuclear abnormalities appeared as chromatin, abnormal shape or absence of microvilli, highly increased amount of smooth endoplasmic reticulum in the cytoplasm and appearance of numerous vacuoles.
d- Biochemical changes where ZnONPs triggered induction of oxidative stress which appeared in the form of increased levels of hydrogen peroxide and inability to activate the detoxifying enzymes alkaline phosphatase (ALP), catalase and glutathione peroxidase (GPX).
e- ZnONPs inhibited the growth rate of the larval gut fauna in vitro.
iii. Amelioration of C. pipens larvae from ZnONPs (application of a 72h recovery period) did not enhance the tested biological signs which clearly indicate that ZnONPs induce chronic actions in C. pipens larvae.