الفهرس 
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Abstract
The present study aimed to evaluate the toxic effect of copper oxide nanoparticles (CuONPs) and silver nanoparticles (AgNPs) and the possible protective effect of ascorbic acid on the parotid gland (PG) of Albino rats histologically and ultrastructurally.
Fifty four male Albino rats weighing between 150 - 200 mg were used in this study.
The animals were divided into the following groups:
I. Control groups (14 rats):
Which were divided to:
a) Subgroup C1: seven Albino rats received IP injection with 2.5 mg/kg body weight (b.w) distilled water three times a week for
6 weeks up to 18 injections.
b) Subgroup C2: seven Albino rats received IP injection with aqueous nitrate buffer in a dose of 2 mg/kg body weight (b.w.) daily for 28 days.
II. Experimental groups (40 rats):
Which were divided to:
a) group I: ten Albino rats received IP injection with CuONPs suspended in distilled water in a dose of 2.5 mg/kg (b.w) three times a week for 6 weeks up to 18 injections.
b) group II: ten Albino rats received IP injection with CuONPs suspended in distilled water in a dose of 2.5 mg/kg (b.w) three
times a week for 6 weeks up to 18 injections, with oral administration of 100 mg/kg (b.w) of vitamin C in drinking water three times a week for 6 weeks.
c) group III: ten Albino rats received 2 mg/kg (b.w) of AgNPs
IP injection daily for 28 days.
d) group IV: ten Albino rats received 2 mg/kg (b.w) of AgNPs IP injection daily for 28 days, with oral administration of 100 mg/kg (b.w) of vitamin C in drinking water daily for 28 days.
After the experimental period, rats were sacrificed by extra dose of anesthesia. The gland was excised and half the specimens were examined by LM and the other half were prepared and examined by TEM.
I. Light microscopic results:
a) Control Groups (C1&C2):
Examination of the PG of both control groups revealed normal histological features of the parenchymal element and connective tissue. The ducts were surrounded by fibrous C.T stroma containing cells, fibers and blood vessels (B.V) and their lumen were empty.
b) group I (CuONPs):
Examination of the H&E stained sections of this group revealed serous acini with ill-defined outline and cytoplasmic vacuolation varying in sizes. Nuclei of the acinar cells appeared
pyknotic and pleomorphic. Some cells showed binucleation and crescent shaped nuclei. Intercalated ducts showed loss of cell height, while striated and excretory ducts showed signs of degeneration and their lumen contained stagnated secretion. Hyalinization of the fibrous C.T surrounding the excretory ducts and presence of congested BVs filled with RBCs were also noted. c) group II (CuONPs with Vitamin C):
The PG of this group showed less cytoplasmic vacuolations compared to CuONPs group. Nuclei of the acinar cells still showed pyknosis, pleomorphism and binucleation. Intercalated ducts showed apparent loss of cell height. Striated and excretory ducts showed apparently empty lumen but retained other signs of degeneration. C.T surrounding the excretory ducts showed hyalinization and congested BVs.
d) group III (AgNPs):
Examination of the H&E stained sections of this group revealed serous acini with ill-defined outline and different sized vacuolations. Nuclei of the acinar cells showed pyknosis, pleomorphism and binucleation. Intercalated ducts showed apparent loss of cell height, while striated and excretory ducts showed signs of degeneration with stagnated secretion filling their lumen. The fibrous C.T surrounding the excretory ducts showed hyalinization as well as presence of congested BVs filled with RBCs.
e) group IV (AgNPs with Vitamin C):
When compared with AgNPs group, PG of this group showed apparently less cytoplasmic vacuolations and some acini appeared apparently normal, while others retained signs of degeneration. Intercalated, striated and excretory ducts still showed signs of degeneration but their lumen appeared empty. Hyalinization of the C.T surrounding the excretory ducts and congested BVs were still present.
II. Electron microscopic results:
a) Control Groups (C1&C2):
Electron microscopic examination of control groups revealed serous acini with normal intracellular structure. Secretory granules of moderate electron density located apically, normal mitochondria and rough endoplasmic reticulum (RER) were observed in the acinar and ductal cells.
b) group I (CuONPs):
Electron microscopic examination of the PG of this group revealed that acinar cells showed pleomorphic nuclei and different sized cytoplasmic vacuolations. Organelles showed signs of degeneration, RER cisternae appeared dilated and mitochondria appeared swollen with damaged cristae. Lysosomes were filled with electron-dense NPs. Nuclei and organelles of intercalated, striated and excretory ducts showed signs of degeneration.
c) group II (CuONPs with Vitamin C):
The PG of this group showed acinar cells with less cytoplasmic vacuolations surrounding a narrow lumen and secretory granules with moderate density located apically. Nuclei appeared apparently normal while others showed binucleation. Apparently normal mitochondria and less lysosomes were seen but RER cisternae appeared dilated. Intercalated duct showed normal nuclei and mitochondria with apparently less number of lysosomes filled with NPs. Striated and excretory ducts showed nuclei with different size and shape and apparently empty lumen. Cells also showed normal mitochondria, less cytoplasmic vacuolations and apparently less lysosome filled with electron- dense NPs were noticed.
d) group III (AgNPs):
Electron microscopic examination of PG of this group showed acinar cells with different sized nuclei and different sized cytoplasmic vacuolation. Organelles showed signs of degeneration, the lysosomes were filled with AgNPs, mitochondria were swollen with damaged cristae and cisternae of RER were dilated. Nuclei and organelles of intercalated, striated and excretory duct cells showed the same signs of degeneration in addition to stagnated secretion.
e) group IV (AgNPs with Vitamin C):
Compared to AgNPs group, PG of this group showed
Apparently normal nucleus and secretory granules of moderate density situated apically. RER and mitochondria appeared normal with less cytoplasmic vacuolation and lysosomes filled with electron-dense NPs. Intercalated duct showed apparently normal nuclei, cytoplasmic vacuolation, normal mitochondria and RER with less lysosomes. Striated and excretory duct cells showed pleomorphic nuclei, less cytoplasmic vacuolation and lysosomes with normal mitochondria and RER.
III. Statistical analysis
• A highly significant decrease in the mean surface area of serous acini was recorded between CuONPs group and control group (P1<0.001).
• Comparing CuONPs with vitamin C group to CuONPs group
showed a significant increase in the mean surface area of acini
(P3=0.02).
• A highly significant decrease in the mean surface area of serous acini was recorded between AgNPs group and control group (P1<0.001).
• Comparing AgNPs with vitamin C group to AgNPs group
showed a significant increase in the mean surface area of acini
(P3=0.002).
• Comparing CuONPs group to AgNPs group showed a non- significant decrease in the mean surface area of acini (P3=0.4).