Biofiltering capacity of Chambardia rubens (Bivalvia: Unionidae) may modulate expression of stress and growth genes inhibited by the neonicotinoid insecticide acetamiprid in zebrafish.

Neonicotinoid insecticides specifically target insect subtypes of nicotinic acetylcholine receptors. Acetamiprid (ACE: C10H11ClN4), the neonicotinoid insecticide, is used to control crop insect pests worldwide. It is a nitrile, monochloropyridine, and carboxamidine that is highly soluble and accessible to waterways. There, it causes neurotoxic and oxidative perturbance to non-target organisms. The unionid mussel Chamabradia rubens is a common Northern River Nile suspension feeder. The current study aimed to assess ACE filtration from waters by C. rubens, and whether this biological power can reduce ACE effects on fish. Removal of ACE by C. rubens was assessed using LC-MS/MS. Zebrafish Danio rerio adults were exposed to different sublethal doses of ACE in the presence or absence of C. rubens in their aquaria. The results showed that mussels could remove significant ACE amounts from water, where it accumulated mostly in the digestive gland. The presence of C.rubens in zebrafish aquaria having ACE was accompanied by significant upregulation of antioxidant enzyme gene transcripts and total H2O2 scavenging, in contrast to mussel-free ACE-exposed groups. Meanwhile, liver triglycerides rose 5-6-fold in response to ACE in the "Fish-Only" groups, indicating an ACE-induced hepatotoxicity. Also, Insulin-like growth factor 1 (igf1) and fish body mass increased more in "Fish + Mussel" groups than in the "Fish-Only" ones. In aggregate, these findings suggest that the Nile mussel could reduce the oxidative stress and metabolic changes induced in fish by ACE. This can contribute valuable environmental and economic benefits upon the use of this mussel as a biofilter.

Immunosuppressive effect of cyclophosphamide in Nile tilapia (Oreochromis niloticus).

Cyclophosphamide, a common chemotherapeutic and immune suppressor agent, is regularly used in research to weaken the immune system in laboratory animal models. Nile tilapia (Oreochromis niloticus) is a widely used experimental fish model for immune-modulatory research; with the lack of knowledge about the immune-compromised tilapia model, an urgent need is to develop and optimise such a model. Sixty healthy Oreochromis niloticus fish, average weight 50 ± 10 g, were divided into four experimental groups. Fish in group I, negative control group, were injected with phosphate-buffered saline only, and fish in groups II, III and IV were injected with cyclophosphamide (CP) at 100, 200 and 400 mg/kg body weight (BW), respectively, via the intraperitoneal route. Different immune-related parameters were investigated 3 weeks after CP injection. The results have revealed a significant decrease in total red blood cells (RBCs), white blood cells (WBCs) and thrombocyte counts and reduced haemoglobin and haematocrit values in CP-treated fish, especially those injected with 200 mg/kg BW compared with the control group (p < 0.05). Also, significantly lower levels of serum proteins (total protein, albumin, α1- and γ-globulins) were observed in CP-treated fish, especially those injected with 200 mg/kg BW in comparison with the control group (p < 0.05). Furthermore, CP-treated fish showed a reduction in the expression of immune-related genes (interleukin-1, and tumour necrosis factor-α in spleen and tumour necrosis factor-α and transforming growth factor ß-1 in head-kidney), especially those injected with 200 mg/kg BW compared with the control group (p < 0.05). In conclusion, the Oreochromis niloticus immune-suppressed model can be induced by intraperitoneal CP injection at 200 mg/kg BW.

Pathological and immunohistochemical studies following the experimental infection of ayu (Plecoglossus altivelis) by Edwardsiella ictaluri.

In recent decades, several mass mortalities were recorded in riverine ayu (Plecoglossus altivelis) in Tokyo Metropolis, Hiroshima Prefecture, and Yamaguchi Prefecture, Japan; in these outbreaks, microbiological and pathological examinations revealed Edwardsiella ictaluri as the causative agent. In this study, histopathological findings and immunohistochemical localization of the bacteria following experimental infection of ayu were discussed. Infection experiments were performed using 44 healthy cultured ayu fingerlings using E. ictaluri isolate (H90). The fish were injected with the isolate intraperitoneally with a dose of 5.1 × 105 cfu/fish, while the control fish were injected with sterile phosphate buffered saline. The fish were observed for clinical signs, with daily collection of dead fish, and isolation of bacteria from the posterior kidney was performed and confirmed to be E. ictaluri by slide agglutination using anti-PH0744 serum. Daily collection of five moribund fish for necropsy and tissue specimens collection from hepatopancreas, spleen, posterior kidney, gills, brain, heart, and intestine for histopathological and immunohistochemical examination. Post-mortem lesions were recorded as exophthalmia, bloody ascitis, hemorrhagic kidney and distended gallbladder, meningio-encephalitis, hemorrhagic vent, and petechial hemorrhages on viscera. Histopathological examination revealed diffuse severe congestion in blood vessels and several degenerative and necrotic changes inconcurrent with positive antigenic staining by immunohistochemistry.

Molecular characterization and immunohistochemical localization of tilapia piscidin 3 in response to Aeromonas hydrophila infection in Nile tilapia.

The antimicrobial activity of tilapia piscidin 3 (TP3) was determined in vitro against a locally isolated Aeromonas hydrophila. A 388 bp fragment was amplified from the TP3 cDNA and sequenced. The coding sequence (CDS) of TP3 was estimated to be 231 bp codes for 76 amino acids long and stop codon. In silico analysis was performed to detect both the signal peptide and the prodomain cleavage sites to follow the amino acids number 22 and 70, respectively. Based on this, a peptide 23 amino acids long with a remarkably high computed antimicrobial probability was synthesized and used in the subsequent experiments. The antimicrobial activity of TP3 was determined with minimum inhibitory concentration (MIC) and minim um bactericidal concentration (MBC) methods. TP3 exhibited relatively weak antimicrobial activities against the tested bacteria. A challenge experiment was then performed in Nile tilapia with low and high doses of A. hydrophila, followed by timely recognition; after 3, 6, 24 h, and 7 days of the specific TP3 gene expression, immunohistochemical localization was also performed. Histopathological examination revealed provoked inflammatory responses and congestion in the same organs of TP3 expression. Immunohistochemical localization showed that A. hydrophila induced tilapia fish to express TP3 after 24 h within the gills, intestine, hepatopancreas, spleen, and posterior kidney. In quantitative real time (RT)-polymerase chain reaction analysis, the high dose showed higher mRNA expression levels than the low dose, and its expression levels increased in the A. hydrophila-infected fish. It was therefore concluded that TP3 plays an essential role in fish immunity.

Piscidin 4: Genetic expression and comparative immunolocalization in Nile tilapia (Oreochromis niloticus) following challenge using different local bacterial strains.

The antimicrobial activity of tilapia piscidin 4 (TP4) was determined in vitro against four bacterial strains, Aeromonas hydrophilla, Pseudomonas fluorescens, Streptococcus iniae and Vibrio anguillarum. Nile tilapia were infected with low and high doses of the tested pathogens; after 3, 6, 24 h and 7 days of the specific TP4 gene expression, tissue immunolocalization was also performed. Histopathological examination revealed septicaemia and necrosis of hemopoietic tissue for all of the tested bacteria. Immunolocalization showed abundance in S. iniae-infected fish tissues. Quantitative RT-PCR analysis revealed that high doses raised mRNA expression levels compared to low doses and expression levels increased in the infected fish, particularly after 24 h, indicating that TP4 exerts potent bactericidal activity against some fish pathogens and plays an essential role in fish immunity.

The protective role of spirulina and ß-glucan in African catfish (Clarias gariepinus) against chronic toxicity of chlorpyrifos: hemato-biochemistry, histopathology, and oxidative stress traits.

Chlorpyrifos (CPF) is an insecticide that is commonly applied in the agriculture sector. However, little is known about the protective role of Spirulina platensis (SP) and/or ß-glucan (BG) on African catfish exposed to chronic CPF toxicity. The fish (95 ± 5 g, initial weight) were assigned to 5 fiberglass tanks (500 L, 50 fish/tank) where the 1st and 2nd fed the basal diet, while the 3rd, 4th, and 5th fed diets with SP, BG, and SP+BG at 0.5%, respectively. Fish in 2nd, 3rd, 4th, and 5th groups were exposed to CPF at a dose of 1.5 mg/L and fed the respective diets for 60 days. In comparison with the control group, CPF-exposed fish exhibited significantly lower (P ≤ 0.05) body weights, feed intake, red blood cells count, hemoglobin concentration, packed cell volume (PCV) (%), lymphocytes, monocytes, phagocytic activity, and phagocytic index, while feed conversion ratio, white blood cell count, and neutrophils count were significantly increased. Fish exposed to CPF also revealed a significant elevation in aspartate aminotransferase (AST), alanine aminotransferase (ALT), cholesterol, triglycerides, low-density lipoproteins (LDL), very-low-density lipoproteins (vLDL), glucose concentration, urea, and creatinine as well as low total proteins, albumin, globulins, and high-density lipoprotein (HDL) concentration. Fish exposed to CPF also exhibited a high concentration of malondialdehyde while glutathione content, glutathione peroxidase, and catalase activities were significantly decreased in the liver, gills, brain, and intestine tissues. Moreover, exposure to CPF resulted in higher transcription of cytochrome P450 (CYP1A-P450) gene expression than the 1st group. Histopathological investigations revealed various degrees of pathological lesions in different organs like the liver, kidney, brain, spleen, and intestine tissues. Interestingly, dietary SP supplementation either alone or combined with BG significantly ameliorated the alterations mitigated by CPF-induced organ injuries and genotoxicity. Therefore, it could be concluded that SP or/and BG are able to induce the protective consequences on health status, immunity, and antioxidative response of African catfish exposed to CPF.

Comparative immunohistological study on using capsaicin, piperine, and okadaic acid for the transepithelial passage of the inactivated viral and bacterial vaccines in fish.

The practical difficulty of parenteral application of fish vaccines against devastating fish diseases diverted the interest toward oral vaccination. Search for effective methods to enhance the oral uptake of viral and bacterial vaccines is continuing. The current research focus on a new role of mucosal fish vaccine adjuvants inducing the antigen uptake by enhancing vascularity or increasing intestinal permeability. Some inflammatory substances cause reversible pathology to the intestinal epithelium, which could be employed for the transepithelial passage of vaccine particles. The natural inflammatory substances used were capsaicin, piperine, and okadaic acid as 1 mg, 2 mg, and 1 µg/fish, respectively. Two inactivated vaccines were used as antigens to test the effect of these inflammatory substances in two different fish hosts. Tested vaccines were inactivated redspotted grouper nervous necrosis virus vaccine in sevenband grouper (Epinephelus septemfasciatus) and inactivated Edwardsiella tarda vaccine in red sea bream (Pagrus major) fish models. The inflammatory substances and each vaccine were anally intubated to fish. Capsaicin proved to be effectively aiding the transepithelial passage of vaccine particles more than piperine, while okadaic acid had no detectable effect.

A novel jumbo Tenacibaculum maritimum lytic phage with head-fiber-like appendages.

A novel jumbo bacteriophage (myovirus) is described. The lytic phage of Tenacibaculum maritimum, which is the etiological agent of tenacibaculosis in a variety of farmed marine fish worldwide, was plaque-isolated from seawater around a fish aquaculture field in Japan. The phage had an isometric head 110-120 nm in diameter, from which several 50- to 100-nm-long flexible fiber-like appendages emanate, and a 150-nm-long rigid contractile tail. The full genomes of the two representative phages (PTm1 and PTm5) were 224,680 and 226,876 bp long, respectively, both with 29.7% GC content, and the number of predicted open reading frames (ORFs) was 308 and 306, respectively. The average nucleotide sequence identity between PTm1 and PTm5 was 99.95%, indicating they are quite similar to each other. A genetic relationship was found in 15.0-16.6% of the predicted ORFs among the T. maritimum phages PTm1 and PTm5, the Tenacibaculum spp. phage pT24, and the Sphingomonas paucimobilis phage PAU. Phylogenetic analysis based on the terminase large subunit genes revealed that these four phages (PTm1, PTm5, pT24 and PAU) are more closely related than the other 10 jumbo myoviruses that have similar genome sizes. Transmission electron microscopy observations suggest that the head fibers of the T. maritimum phage function as tentacles to search and recognize the host cell surface to facilitate infection.

Metals concentrations in Nile tilapia Oreochromis niloticus () from illegal fish farm in Al-Minufiya Province, Egypt, and their effects on some tissues structures.

This study clarified the suitability of fishes caught from illegal fish farms to human consumption and their hazards to public health. For this purpose, the concentrations of some metals (Al, Cd, Pb, Hg and Ni) in water and Nile tilapia (Oreochromis niloticus) fish samples collected from an illegal fish farm, in addition to pathological conditions of the fish tissues, were examined. The illegal farm water was found to be heavily polluted with metals which far exceeded the permissible limits. It was found that metals accumulated in tissues of O. niloticus in concentrations higher than those of farm water. Kidney of O. niloticus contained the highest concentrations of the detected metals, while muscle and skin contained the lowest concentrations. The examination of fish tissues revealed various histopathological lesions which related directly to the pollution of the illegal farm water. Moreover, metals levels in O. niloticus muscle were higher than the maximum permissible levels for human consumption. Consequently, the flesh of fishes from the illegal farms could be considered hazardous to human health. Therefore, warning against eating fish caught from the illegal fish farms should be announced. Moreover, removal of such illegal fish farms is necessary for the public health protection.