الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
 |  | from | 159 |  |  |
| | | from | 159 | | |
Abstract
Plastic pollutants are a serious environmental problem due to their size and persistence in the environment. The use of plastic includes almost all aspects of modern life, including packaging, construction, automobiles, electronics, electrical appliances, clothing, agriculture, etc. Plastic nanoparticle pollution is a significant issue nowadays due to its direct impact on environmental health and public safety.
The present study was designed to evaluate:
• The effect of exposure to NPs on C. gariepinus this was carried out by investigating, serum biochemical measurements (Oxidative stress status, AST and ALT enzymes ), detection of DNA damage in blood of catfish, estimation of micronucleus, other nuclear abnormalities and erythrocyte alterations and histopathological investigations that NPs may induce in the liver and kidney of C. gariepinus.
• The ameliorative role of selenium and C. vulgaris against Ps NPs induced hepatotoxicity, nephrotoxicity, genotoxicity and cytotoxicity in catfish.
A total number of one hundred and forty-four male late juvenile Catfish (Clarias gariepinus) were randomly distributed to six groups (n= 24/group, three replicate) as follows:
1- First group (C): kept as control which fish received water free of Polystyrene nanoplastics.
2- Second group (NP): exposed to 5 mg/L polystyrene nanoplastics in water.
3- Third group (NP+Se): exposed to polystyrene nanoplastics (5 mg/L) + selenium (1 mg/kg diet).
4- Fourth group (NP+Ch): exposed to polystyrene nanoplastics (5mg/L) + C. vulgaris (25 g/kg diet ).
5- Fifth group (Ch): received only C. vulgaris (25 g/kg diet).
6- Sixth group (Se): received only selenium (1 mg/kg diet).
The exposure was for 30 days to all groups.
Six fish from the control and treatment groups, were randomly caught using hand net and euthanized by using ice to minimize stress. Blood samples were collected from the caudal vein of C. gariepinus in vacutainer tubes coated with (EDTA) for detection of DNA damage.
Another blood samples were taken in vacutainer tubes without anticoagulant and centrifuged at 3000 rpm for 15 min to obtain serum which was stored at -20°C for estimation of biochemical parameters.
Blood smears were prepared and fixed in absolute methanol after drying in room temperature for micronuclei test.
The study revealed that NPs has been recommended to enhance the oxidative stress by elevating the malondialdehyde representing lipid peroxidation in C. gariepinus serum.
The obtained results revealed that exposed to NPs showed a significant increase in all DNA damage parameters (tail length, tail DNA %, tail moment and Olive tail moment) associated with increased MDA level and mild decrease of the antioxidant levels. Also significant increase in MN frequency and several erythrocyte alterations.
The histological findings of hepatic tissues of NPs-intoxicated C. gariepinus demonstrated the hepatotoxic effects of NPs that consisted of fatty degeneration and change (micro and macrovesciular steatosis) of heptocytes. Other hepatic cells showed coagulative necrosis with nuclear changes. Disorganization of the hepatic cord was also observed. Pericentral fibrosis and periportal fibrosis were also detected and an increased amount of connective tissue around the biliary ductiles and portal veins were also seen. These connective tissue proliferations were confirmed by the specific stains Picrosirius red and Gomori’s trichrome. PAS+Hematoxylin stained paraffin liver sections showed a depletion and a decrease of PAS-positive glycogen granules in the affected liver cells as a response of nanoplastics intoxication.
The nephrotoxic effects of nanoplastics were also studied in this experiment and H&E stained kidney sections from the NPs-intoxicated catfish showed several pathological changes that consisted of vacuolar degeneration, apoptosis and coagulative necrosis of cells lining the renal tubules, that later dissociated causing detachment of the tubular epithelium. Peritubular fibrosis around the renal tubules and tubular dilatation were also detected. Renal blood vessels were also affected and showed presence of perivascular fibrosis and thrombosis
Administration of C. vulgaris and selenium to the diet of NPs-Chlorella vulgaris treated and NPs+selenium of catfish significant decrease lipid peroxidation and improved the general state of catfish, the liver function test, also alleviated the hepatotoxic and nephrotoxic effects of NPs and restored the histological appearances.
It could be concluded that the exposure to NPs induced DNA damage, erythrocyte alterations, biochemical and histopatholgical changes. While supplementation of selenium or C. vulgaris were lead to ameliorative effects against NPs induced toxicity through their antioxidant properties and reduction of lipid peroxidation. Therefore, this study suggested that supplementation of selenium and C. vulgaris as feed supplements in fish diet to protect against environmental pollutants by NPs.