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Ohta T.,Ehime University | Ueda Y.,Ehime University | Ito K.,Ehime University | Miura C.,Ehime University | And 3 more authors.
Fish and Shellfish Immunology | Year: 2011

Interferon (IFN) plays crucial roles in innate immune responses against viral infections. In the present study, we report cloning and characterization of the IFN gene from the sevenband grouper (Epinephelus septemfasciatus), and the anti-viral effects of its recombinant IFN protein in vivo. The isolated cDNA from sevenband grouper IFN encoded a protein consisting of 178 amino acids, and its first 22 amino acids represented a putative signal peptide. We named the identified sevenband grouper IFN gene as SgIFNa1 based on the result from phylogenetic analysis that categorized the deduced protein sequence into fish IFNa family. The expression of SgIFNa1 mRNA in the head kidney cells was induced by synthetic Poly(I:C), which is known as an inducer of IFN. It has also been confirmed that injection of recombinant SgIFNa1 protein (rSgIFNa1) upregulates expression of the Mx gene, which is known as an IFN-responsive gene, in head kidney cells. Moreover, we observed that preliminarily injection of rSgIFNa1 provided significant protection against a lethal challenge of nervous necrosis virus (NNV), which is a serious disease of sevenband grouper. These results demonstrate that SgIFNa1 has anti-viral activity and the administration of rSgIFNa1 to sevenband grouper is effective in preventing severe symptom development after NNV infection. © 2011 Elsevier Ltd. Source


Takagi S.,Ehime Prefectural Fisheries Experimental Station | Takagi S.,Ehime Fisheries Research Center | Murata H.,University of Miyazaki | Hatate H.,University of Miyazaki | And 4 more authors.
Fisheries Science | Year: 2011

This study was conducted to investigate the mechanism of green liver symptom induction and the effect of dietary taurine supplementation on growth performance in juvenile red sea bream fed non-fishmeal diets based on soy protein concentrate (SPC). Juvenile fish (initial BW 72 g) were fed for 20 weeks on SPC diets supplemented with taurine at levels of 0, 1.0, and 2.0%. In the taurine-unsupplemented SPC diet group, specific growth rate (SGR) and feed conversion ratio (FCR) were significantly inferior (P < 0. 001), and incidence of green liver was observed in 70% of fish. In this group, hepatopancreatic and plasma taurine concentrations were lowest (P < 0.05), hepatopancreatic content of bile pigments was highest (P < 0.05), and osmotic tolerance of erythrocytes was inferior (P < 0.05) among the dietary treatment groups. Serum osmolality of all treatment groups was at similar levels. These physiological abnormalities as well as SGR and FCR were improved by dietary taurine supplementation. These results indicate that the mechanism for induction of green liver symptom is bile pigment overproduction due to increased hemolysis because erythrocytes become osmotically fragile due to dietary taurine deficiency. Taurine supplementation of SPC diets is essential for maintaining normal physiological condition and growth performance in juvenile red sea bream. © 2011 The Japanese Society of Fisheries Science. Source


Yokoyama H.,University of Tokyo | Yanagida T.,Asahikawa Medical College | Freeman M.A.,University of Malaya | Katagiri T.,Tokyo University of Marine Science and Technology | And 4 more authors.
Journal of Fish Diseases | Year: 2010

Mass mortality of cultured yellowtail, Seriola quinqueradiata, has recently been reported from fish farms in western Japan. Previous studies revealed that diseased fish were characterized by encephalomyelitis and presporogonic stages of a myxosporean-like parasite in the spinal cord. However, the parasite has remained unidentified because of the lack of mature stages being present. Thus, in the present study, analysis of the small subunit ribosomal DNA (18S rDNA) of the parasite as well as in situ hybridization (ISH) studies using histological sections of the infected tissue was conducted. The 18S rDNA of the myxosporean had higher sequence similarities with those of bile-duct-infecting myxosporeans rather than those infecting nervous tissues and was identified as Myxobolus spirosulcatus. The ISH using specific probes demonstrated that the DNA amplified was derived from the multinuclear organisms found in histological sections. A highly sensitive and specific PCR-based assay for M. spirosulcatus was developed, which revealed a high prevalence of infection in cultured yellowtail that exhibited the clinical signs of encephalomyelitis. © 2010 Blackwell Publishing Ltd. Source


Yokoyama H.,University of Tokyo | Meng F.,University of Tokyo | Hirai M.,Ehime Prefectural Fisheries Experimental Station | Takagi S.,Ehime Prefectural Fisheries Experimental Station | And 2 more authors.
Journal of Aquaculture Research and Development | Year: 2011

Encephalomyelitis associated with developmental stages of a myxosporean parasite has recently occurred in cultured yellowtail Seriola quinqueradiata from western Japan. Although mature spore stages of the parasite were not found in the spinal cord, the myxosporean was molecularly identified as Myxobolus spirosulcatus by the 18S rDNA analysis and in situ hybridization and has been previously reported as a non-pathogenic parasite infecting the bile duct of yellowtail. However, the causal relationship between the encephalomyelitis and M. spirosulcatus is still controversial. Typical signs of the disease were reduced feeding, erratic and abnormal swimming, skin ulceration from the jaw to the abdomen, and redness of the brain. Histopathologically, this disease was characterized by 1) gliosis and multi-focal glial nodules, 2) nerve cell necrosis with neurophagia, 3) blood congestion and hemorrhages in the central nervous tissue, 4) swollen eosinophilic nerve fibers and degenerative axons. In the present study, we conducted further histopathological observations and tried to determine the disease mechanisms in relation to water temperature and feeding regimes. It was indicated that developing plasmodia directly caused the gliosis and glial nodules in the nervous system. Fluctuating water temperature was suggested to be partly responsible for disease outbreak. Detection rates of M. spirosulcatus spores in the bile were signifcantly higher in the constant temperature groups than those in the fluctuating temperature groups. Further studies on the biology of M. spirosulcatus are required to implement a management strategy to the myxosporean encephalomyelitis of yellowtail. © 2011 Yokoyama H, et al. Source


Kondo R.,Fukui Prefectural University | Shigematsu K.,Fukui Prefectural University | Kawahara N.,Fukui Prefectural University | Okamura T.,Fukui Prefectural University | And 4 more authors.
Fisheries Science | Year: 2012

The abundance of sulphate-reducing bacteria (SRB) was investigated in the coastal marine sediments along the coast of Japan and South Korea. Sediment samples were collected from fish and shellfish farms between 2006 and 2008. As non-fish farming reference sites, sediments were also collected from highly eutrophic bays, a highly sulphidogenic saline lake, and the deep sea. A quantitative real-time PCR analysis that targeted the gene coding for a portion of the α-subunit of dissimilatory sulphite reductase (dsrA) was performed to assess the abundance of the SRB in the sediments. Between 2. 8 × 10 7 and 2. 5 × 10 9 copies of the dsrA gene per gram dry sediment were detected. There was no relationship between dsrA gene copy number and total bacterial count in the sediments, whereas organic matter contents (particulate organic carbon and nitrogen, ignition loss and chemical oxygen demand) and acid-volatile sulphide contents were significantly correlated with the dsrA copy number. The data presented demonstrate that organic enrichment of sediment may influence the abundance of SRB communities in coastal marine sediments and that the cell density of SRB may be used as a biological indicator for assessing pollution levels in sediments of marine fish farms. © 2011 The Japanese Society of Fisheries Science. Source

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