الفهرس 
Acknowledgments
Characterization of the silver nanoparticles (AgNPsOnly 14 pages are availabe for public view
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Abstract
In the present study 72 specimens of Clarias gariepinus were used to determine the adverse effect of size (20 nm & 40 nm) and concentrations (10 µ g/L & 100 µ g/L) of silver nanoparticles and concentration of silver nitrate (100 µ g/L) on behavioral changes, mortality, growth performance (condition factor and hepatosomatic index), blood constituents (erythrocyte count, haemoglobin, haematocrit, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, white blood cells, glucose, total lipids, total proteins, albumin, globulin, albumin /globulin ratio, ALT, AST and ALP enzymes and erythrocyte alterations), hormones (testosterone and 17β- estradiol), antioxidant enzymes (lipid perioxidation, Catalase, superoxide dismutase, glutathione-s-transferase) on liver tissues. Also, comet assay on blood cells and accumulation of silver nanoparticles on tissues (liver, gills and muscles). Also, histopathological and histochemical characteristics of the liver, kidney, gills and muscles were studied.
The results can be summarized in the following points:
I- Biological and biochemical changes
1- Behavioral changes
After 15 days of fish exposure to silver nanoparticles and silver nitrate showed abnormal behavior such as nervous manifestation, change in color, loss of appetite and fins stretching. Moreover, after 15 days of recovery period fishes were noticed in better conditions and no mortality was recorded in all treatments.
2- Growth performance
Condition factor (CF) and hepatosomatic index (HSI)
The size and concentration of AgNPs and their interactions exhibited no significant variations in CF during exposure and recovery periods whereas HSI was affected by the AgNPs size during the exposure period only.
3- Blood constituents:
A- Haematological parameters
• RBCs, HCT, MCHC and WBC were significantly affected by silver nanoparticles size, whereas RBC, HB, HCT and WBC were significantly affected by silver nanoparticles concentration. In the recovery period, only RBCs, HCT, MCV, MCH and MCHC were still impacted by the nanoparticle size and RBCs, HB, HCT and WBC were stressed by these particle concentration.
B- Erythrocytes alterations
• The erythrocytes showed morphologically, different patterns of deformed cells in AgNPs-induced fish of C. gariepinus. These patterns include Acanthocytes (Ac), Echinocytes or Crenated cells (Cr), Tear drop-like cells (Tr), Sickle cells (Sk), Target cells (codocytes or leptocytes) (T), Eliptocyte (EL), Keratocyte (Kr), Swelled cells (Sc), Vacuole cells (Va) and Ovalocyte (Ov). ). Recovery period for 15 days shows normal shape of erythrocyte as the control group.
C. Comet assay
• The DNA damage of erythrocytes was increased significantly (P<0.001) after exposure of Clarias gariepinus to AgNPs compared to control fish.
• The main effects of treatments and classes were significant in all parameters.
• In the recovery period, the main effects of treatments and classes were significant in all parameters except for TDNA.
• In comparison to the control group, the DNA damage of the nanoparticle-exposed fish exhibited significant variability in all parameters.
• After 15-day recovery, the pollutant adverse effects on the DNA damage were still recorded to some extent in comparison to the control group.
D. Biochemical parameters
• Serum glucose and the total lipid levels showed a significant increase in fishes exposed to AgNPs and AgNO3. Recovery period not corrected markedly the levels of glucose and total lipids in comparison with the control.
• Serum total protein, albumin, globulin and albumin/globulin ratio levels showed a significant decrease in fishes exposed to AgNPs and AgNO3. Recovery period for 15 days led to improvement of levels of theses parameters.
• ALT, AST and ALP activities showed a significant increase in fishes exposed to AgNPs and AgNO3. On the recovery period significant variability was recorded except for AST activities in comparison to the control and silver nitrate groups.
• The creatinine and uric acid levels showed a significant increase in fishes exposed to AgNPs and AgNO3. Recovery period improved level of creatinine and uric acid compared to the control level.
4- Effect on enzymes activities
• LPO contents in the liver tissue of Clarias garepinus exposed to AgNPs showed a significant increase compared with control group after 15 days exposure and 15 days recovery periods.
• CAT, SOD and GST activities showed a significant decrease in the liver tissues of Clarias garepinus exposed to AgNPs. Recovery period improved level of CAT, SOD and GST compared to the control level.
5- Hormonal Measurements
• Serum testosterone and 17β - estradiol levels showed a significant decrease in fishes exposed to AgNPs and AgNO3. Recovery period improved level of testosterone and 17β - estradiol compared to the control level.
6- Determination of silver concentrations in fish tissues
• Maximum AgNPs accumulation was observed in liver, gills and muscles tissues in the exposure period for 15 days. Recovery period did not reduce silver nanoparticles from tissues.
π- Histopathological and histochemical observations
The study included light microscopic detailed descriptions of the histopathological and histochemical characteristics of the liver, kidney, gills and muscles of Clarias gariepinus in the normal condition and after exposure to different size and concentration of silver nanoparticles and silver nitrate for 15 days exposure and 15 days recovery period.
1- Liver
Exposure of fish Clarias gariepinus to 100 µg/L of silver nitrate showed histopathological and histochemical changes:
• The hepatocytes are delimited by ruptured cell membranes in some areas and dispersion of cell contents.
• Some hepatocytes were characterized by the absence of nuclei while the others were having pyknotic nuclei.
• Cytoplasmic vacuolation.
• Infiltration of the inflammatory cells inside the central vein and between the hepatocytes.
• Proliferation of hepatocytes (crowded of nuclei) and an aggregation of melanomacrophage.
• Moderate alterations were observed in the liver tissue and damage percent was 64.5%.
• Accumulation of connective tissue fibers around the central vein and blood sinusoids.
• Accumulation of melanomacrophage beside the central vein and necrotic area.
• A remarkable depletion in the glycogen content in hepatocyte.
Exposure of Clarias gariepinus to 10 µg/Lof silver nanoparticles (20 nm) showed histopathological and histochemical changes:
• The hepatocytes lost their normal polygonal shape and boundary between cells became invisible.
• Sinusoidal lumen was collapsed and few Küpffer cells.
• Rupture of hepatocyte membranes and proliferation of the hepatic cells with a decrease in cell size.
• Infiltration of the inflammatory cells inside the blood vessels and between the hepatocytes and an aggregation of melanomacrophage beside central vein.
• Dilation in the blood vessel and areas of hepatic necrosis started to appear in some regions and rupture of the wall of the central vein.
• Some of hepatocytes were characterized by the absence of nuclei (Apoptotic cell) while the others were having pyknotic nuclei.
• Accumulation of connective tissue fibers around the central vein and blood sinusoids and infiltration of inflammatory cell with necrotic area.
• An accumulation of melanomacrophage between connective tissue.
• A remarkable depletion in the glycogen content in hepatocyte.