Electrical Characterization of Epoxy Nanocomposite under High DC Voltage.

This work studies the direct current breakdown characteristics of unfilled epoxy and epoxy nonconductive nanocomposites (SiO2,MgO and Al2O3). It also examines the variation of electrical properties in epoxy nanocomposites. The novel aspect of this study is that the samples of Epoxy nanocomposite were exposed to high voltages of up to six kilo volts for three hours using field electron microscopy under high vacuum conditions (10-5 mbar). The current emitted from these samples was measured at three different intervals of time. In addition, the influence of high voltage on the permittivity, loss factor (tan(δ)), and conductivity of the epoxy nanocomposite was studied. This evaluation was conducted before and after applying the voltage at room temperature, The frequency range extends from 10-2-10-7 Hz using the Novo Control Alpha-A analyzer. Current-voltage characterization was performed through field electron microscopy. The samples were characterized by scanning electron microscopy-energy dispersive X-ray spectroscopy and Fourier Transform Infrared Spectroscopy. The unfilled epoxy exhibited structural degradation, resulting in the formation of holes when exposed to high voltages of up to six kilo volts, leading to a reduction in electrical properties. Nevertheless, the addition of nanoparticles shows a significant increase in the operational lifetime of the epoxy nanocomposite. The degree of increase in the lifetime of epoxy composite varied depending on several factors such as the type of NPs introduced and their respective sizes. The epoxy/Al2O3 nanocomposite comparing with epoxy/MgO and epoxy/SiO2 nanocomposite showed elevated resistance to direct current breakdown strength and maintaining its dielectric.

Chitosan nanoparticles alleviated endocrine disruption, oxidative damage, and genotoxicity of Bisphenol-A- intoxicated female African catfish.

Bisphenol-A (BPA) is widely used in production of plastic products. It can reach the ecosystems affecting aquatic organisms most likely fishes. The purpose of this study was to study the toxic effects of BPA on the biochemical variables and oxidative stress in female African catfish, Clarias gariepinus and to estimate the protective role of chitosan nanoparticles (CSNPs) against BPA toxicity. Five groups in triplicates of fish were divided as follows: group I was control, group II was treated with CSNPs (0.66 ml/L), group III was exposed to BPA (1.43 µg/L), group IV was treated with BPA (1.43 µg/L) plus CSNPs (0.33 ml/L), and group V was treated with BPA (1.43 µg/L) plus CSNPs (0.66 ml/L) for 30 days. Blood and liver tissue samples were collected at the end of experiment for the biochemical and oxidative stress biomarkers analyses. Results exhibited that serum Follicle Stimulating Hormone (FSH) and 17-ß Estradiol (E2) were significantly decreased in female catfish. While, serum Testosterone (T.) and Luteinizing Hormone (LH) were increased after exposure to BPA. Marked increment in superoxide dismutase (SOD) and malondialdehyde (MDA) levels of hepatic tissue of catfish exposed to BPA. Furthermore, significant reduction in hepatic catalase (CAT), glutathione peroxidase (GSH-px), total antioxidant capacity (TAC), reduced glutathione (GSH), and glutathione S-transferase (GST) levels were decreased significantly in BPA-exposed catfish compared to the control group. However, administration of female C. gariepinus with the low and high doses (0.33 ml/L and 0.66 ml/L) of CNPs restored the biochemical parameters to be close to the normal values of the control group and also, reduced oxidative stress induced by BPA toxicity. This improvement was evident in fish administrated with the high CSNPs dose (0.66 ml/L) compared to catfish exposed to BPA in group (III). Furthermore, the percentage of hepatic DNA damage was detected in group III exposed to BPA alone. However, it was declined after co- administration with both the low and high doses of CSNPs. The study has revealed that treatment with CSNPs has antagonistic functions against the toxicity of BPA in female African catfish.

Expression of Hsp70, Igf1, and Three Oxidative Stress Biomarkers in Response to Handling and Salt Treatment at Different Water Temperatures in Yellow Perch, Perca flavescens.

Stress is a major factor that causes diseases and mortality in the aquaculture industry. The goal was to analyze the expression of stress-related biomarkers in response to different stressors in yellow perch, which is an important aquaculture candidate in North America and highly sensitive to handling in captivity. Three fish groups were established, each having four replicates, and subjected to water temperatures of 14, 20, and 26°C and acute handling stress was performed followed by a salt treatment for 144h at a salinity of 5 ppt. Serum and hepatic mRNA levels of heat shock protein (hsp70), insulin-like growth factor 1 (Igf1), glutathione peroxidase (Gpx), superoxide dismutase 1 (Sod1), and glutathione reductase (Gsr) were quantified at seven times interval over 144 h using ELISA and RT-qPCR. Handling stress caused a significant down-regulation in Hsp70, Gpx, Sod1, and Gsr at a water temperature of 20°C compared to 14 and 26°C. Igf1 was significantly upregulated at 20°C and down-regulated at 14 and 26°C. Salt treatment had a transient reverse effect on the targeted biomarkers in all groups at 72 h, then caused an upregulation after 144 h, compared to the control groups. The data showed a negative strong regulatory linear relationship between igf1 with hsp70 and anti-oxidative gene expressions. These findings could provide valuable new insights into the stress responses that affect fish health and could be used to monitor the stress.

A novel viral responsive protein (MjVRP) from Marsupenaeus japonicus haemocytes is involved in white spot syndrome virus infection.

A viral responsive protein (MjVRP) was characterized from Marsupenaeus japonicus haemocytes. In amino acid homology and phylogenetic tree analyses, MjVRP clustered in the same group with the viral responsive protein of Penaeus monodon (PmVRP15), showing 34% identity. MjVRP transcripts were mainly expressed in haemocytes and the lymphoid organ. Western blotting likewise showed that MjVRP was strongly expressed in haemocytes and the lymphoid organ. Immunostaining detected MjVRP within the cytosol next to the perinuclear region in some haemocytes. Experimental challenge with white spot syndrome virus (WSSV) significantly up-regulated the mRNA level of MjVRP in the M. japonicus haemocytes at 6 and 48 h. Flow cytometry and indirect immunofluorescence assays revealed that the ratio of MjVRP+ haemocytes significantly increased 24 and 48 h post-WSSV infection. These results suggest that MjVRP+ haemocytes have a supporting role in the pathogenesis of WSSV.

Saprolegniosis in Nile Tilapia: Identification, Molecular Characterization, and Phylogenetic Analysis of Two Novel Pathogenic Saprolegnia Strains.

Saprolegniosis is a fungal infection that leads to huge economic losses in tilapia aquaculture. Saprolegnia spp. are usually implicated as the etiological agents, but their identification is sometimes troublesome and confusing. In this study, two Saprolegnia strains (ManS22 and ManS33) were isolated from Nile Tilapia Oreochromis niloticus suffering from saprolegniosis. Both isolates were characterized morphologically and from internal transcribed spacer (ITS) sequence data. Additionally, both strains were tested for pathogenicity, and they were highly pathogenic and caused cumulative mortalities of 88.9% and 95.6%, respectively. Initially, the two strains were identified, by morphology of sexual and asexual stages, as members of the genus Saprolegnia. For more definitive identification and characterization, the ITS region of the ribosomal RNA genes was amplified and sequenced, and sequences were compared with other known sequences in GenBank. A phylogenetic tree constructed using the neighbor-joining method revealed that the two strains fell into two clusters within the species Saprolegnia parasitica. Cluster 1 included the ManS33 strain and cluster 2 the ManS22 strain. Cluster 1 grouped the ManS33 strain with other S. parasitica stains and shared 97-99% sequence similarity. Cluster 2 contained only the ManS22 strain and shared 93-94% similarity to several reference sequences of S. parasitica strains. Therefore, our findings suggest that ManS22 represents a newly described strain of S. parasitica. Received April 19, 2016; accepted October 27, 2016.