Researchers Database

KITAMURA, Shinichi

    Center for Marine Environmental Studies Associate Professor
Last Updated :2021/03/05

Researcher Information

Research funding number

  • 40448379

J-Global ID

Research Interests

  • 病原性因子   マダイ   マボヤ   ヒラメ   Azumiobodo hoyamushi   Miamiensis avidus   免疫毒性   重油汚染   ビルナウイルス   イリドウイルス   スクーチカ症   マボヤ被嚢軟化症   リンホシスチス病   Virology   Microbiology   Ecology   Fish diseases   

Research Areas

  • Environmental science/Agricultural science / Environmental impact assessment
  • Life sciences / Aquaculture / Fish pathology

Academic & Professional Experience

  • 2003 - 2006  韓国麗水大学校水産生命医学科
  • 2006  - 愛媛大学沿岸環境科学研究センター生態系解析分野
  • 2001 - 2003  Ehime UniversityCenter for Marine Environmental Studies
  • 2003  Ehime UniversityCenter for Marine Environmental Studies
  • 1999 - 2001  株式会社微生物化学研究所


  •        - 1999  Kochi University  農学研究科  栽培漁業学専攻
  •        - 1999  Kochi University  Graduate School, Division of Agriculture
  •        - 1997  Fukui Prefectural University  Faculty of Biotechnology
  •        - 1997  Fukui Prefectural University  Faculty of Bioresources

Association Memberships

  • Society of Environmental Toxicology and Chemistry   THE JAPANESE SOCIETY OF FISHERIES SCIENCE   韓国魚病学会   日本微生物生態学会   日本魚病学会   

Published Papers

  • Nawata A, Hirose E, Kitamura SI
    Diseases of aquatic organisms 129 (3) 207 - 214 0177-5103 2018/08 [Peer-reviewed]
  • Noman Reza MA, Mohapatra S, Shimizu S, Kitamura SI, Harakawa S, Kawakami H, Nakayama K, Sawayama E, Matsubara T, Ohta K, Chakraborty T
    Fish & shellfish immunology 82 286 - 295 1050-4648 2018/08 [Peer-reviewed]
  • Ye RR, Peterson DR, Kitamura SI, Segner H, Seemann F, Au DWT
    Aquatic toxicology (Amsterdam, Netherlands) 203 95 - 106 0166-445X 2018/07 [Peer-reviewed]
  • Shogo Motokawa, Yukie Narasaki, Jun-Young Song, Yoshihiro Yokoyama, Euichi Hirose, Shoko Murakami, Sung-Ju Jung, Myung-Joo Oh, Kei Nakayama, Shin-Ichi Kitamura
    Parasitology International 67 (2) 196 - 202 1873-0329 2018/04 [Peer-reviewed]
     Scientific journal 
    The ciliate Miamiensis avidus causes scuticociliatosis in Japanese flounder Paralichthys olivaceus. We previously reported three serotypes of this ciliate distinguishable by serotype-specific antigenic polypeptides (serotype I, 30 kDa serotype II, 38 kDa serotype III, 34 kDa). In this study, we determined the localization site of the serotype-specific polypeptides in the ciliate and determined the genes encoding the polypeptides, using the isolates IyoI (serotype I), Nakajima (serotype II), and Mie0301 (serotype III). SDS-PAGE and immunoblot analysis of cilia, membrane proteins, and cytoskeletal elements of the ciliates revealed that the polypeptides were abundant in the former two. Scanning electron microscopy of ciliates immobilized by homologous antiserum showed morphological changes in the cilia. These evidences suggested that the polypeptides were ciliary membrane immobilization antigens. The ciliary genes identified showed low identity scores—< 51.5% between serotypes. To differentiate the serotypes, we designed serotype-specific PCR primer sets based on the DNA sequences. The PCR-based serotyping results were completely consistent with conventional serotyping methods (immobilization assay and immunoblot analysis). Twenty of 21 isolates were classified as either serotype I or II, and one isolate was undistinguishable. The combination of species-specific PCR previously reported and three serotype-specific PCR could be useful for identifying, serotyping, and surveillance for occurrences of new serotypes of M. avidus.
  • Yukie Narasaki, Yumiko Obayashi, Sayami Ito, Shoko Murakami, Jun-Young Song, Kei Nakayama, Shin-Ichi Kitamura
    Fish Pathology 53 (1) 1 - 9 1881-7335 2018 [Peer-reviewed]
     Scientific journal 
    Miamiensis avidus is the causative agent of scuticociliatosis in various marine fish species. The virulence factors of the parasite have not been identified, so far. In this study, we examined M. avidus extracellular proteinases (ECPs) as potential virulence factors, using culture supernatants as an ECPs source. We investigated the substrate specificity of ECPs using artificial peptides, and the cytotoxicity of the ECPs was examined using CHSE-214 cells. To elucidate the role of ECPs in ciliate growth, M. avidus was cultured on CHSE-214 cells in the presence of proteinase inhibitors. We detected proteinase activities from the supernatant of M. avidus. Viable CHSE-214 cells decreased significantly in number, when incubated in a medium supplemented with the culture supernatant of M. avidus. The growth of ciliates on CHSE-214 cells was delayed in the presence of PMSF (serine proteinase inhibitor) and E-64 (cysteine proteinase inhibitor). These results suggested that the culture supernatant contained ECPs showing cytotoxicity, and the proteinases facilitated nutrient uptake by the ciliates. Thus, ECPs may be responsible for virulence factors of M. avidus.
  • Roy R. Ye, Drew R. Peterson, Frauke Seemann, Shin-Ichi Kitamura, J. S. Lee, Terrance C. K. Lau, Stephen K. W. Tsui, Doris W. T. Au
    ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH 24 (36) 27687 - 27701 0944-1344 2017/12 [Peer-reviewed]
     Scientific journal 
    Many anthropogenic pollutants in coastal marine environments can induce immune impairments in wild fish and reduce their survival fitness. There is a pressing need to establish sensitive and high throughput in vivo tools to systematically evaluate the immunosuppressive effects of contaminants in marine teleosts. This study reviewed a battery of in vivo immune function detection technologies established for different biological hierarchies at molecular (immune function pathways and genes by next generation sequencing (NGS)), cellular (leukocytes profiles by flow cytometry), tissues/organ system (whole adult histo-array), and organism (host resistance assays (HRAs)) levels, to assess the immune competence of marine medaka Oryzias melastigma. This approach enables a holistic assessment of fish immune competence under different chemical exposure or environmental scenarios. The data obtained will also be useful to unravel the underlying immunotoxic mechanisms. Intriguingly, NGS analysis of hepatic immune gene expression profiles (male > female) are in support of the bacterial HRA findings, in which infection-induced mortality was consistently higher in females than in males. As such, reproductive stages and gender-specific responses must be taken into consideration when assessing the risk of immunotoxicants in the aquatic environment. The distinct phenotypic sexual dimorphism and short generation time (3 months) of marine medaka offer additional advantages for sex-related immunotoxicological investigation.
  • Eitaro Sawayama, Shiho Tanizawa, Shin-Ichi Kitamura, Kei Nakayama, Kohei Ohta, Akiyuki Ozaki, Motohiro Takagi
    MARINE BIOTECHNOLOGY 19 (6) 601 - 613 1436-2228 2017/12 [Peer-reviewed]
     Scientific journal 
    Red sea bream iridoviral disease (RSIVD) is a major viral disease in red sea bream farming in Japan. Previously, we identified one candidate male individual of red sea bream that was significantly associated with convalescent individuals after RSIVD. The purpose of this study is to identify the quantitative trait loci (QTL) linked to the RSIVD-resistant trait for future marker-assisted selection (MAS). Two test families were developed using the candidate male in 2014 (Fam-2014) and 2015 (Fam-2015). These test families were challenged with RSIV, and phenotypes were evaluated. Then, de novo genome sequences of red sea bream were obtained through next-generation sequencing, and microsatellite markers were searched and selected for linkage map construction. One immune-related gene, MHC class II beta, was also used for linkage map construction. Of the microsatellite markers searched, 148 and 197 were mapped on 23 and 27 linkage groups in the female and male linkage maps, respectively, covering approximately 65% of genomes in both sexes. One QTL linked to an RSIVD-resistant trait was found in linkage group 2 of the candidate male in Fam-2014, and the phenotypic variance of the QTL was 31.1%. The QTL was closely linked to MHC class II beta. Moreover, the QTL observed in Fam-2014 was also significantly linked to an RSIVD-resistant trait in the candidate male of Fam-2015. Our results suggest that the RSIVD-resistant trait in the candidate male was controlled by one major QTL closely linked to the MHC class II beta gene and could be useful for MAS of red sea bream.
  • Kei Nakayama, Ryohei Yamashita, Shin-Ichi Kitamura
    MARINE POLLUTION BULLETIN 124 (2) 710 - 713 0025-326X 2017/11 [Peer-reviewed]
     Scientific journal 
    To develop a test for assessing the immunomodulatory effects of chemical pollutants on fish, we evaluated the effects of dexamethasone on the natural host pathogen interaction between common carp (Cyprinus carpio) and Aeromonas salmonicida. Carp were exposed to 1 mg L-1 dexamethasone for the entire experimental period. One week after the exposure test started, the exposed fish, as well as unexposed fish, were bath-infected with A. salmonicida. One hundred percent mortality was observed in bacteria-infected fish exposed to dexamethasone, whereas no infection-associated mortality was observed in infected fish in the absence of dexamethasone exposure. In a separate experiment, dexamethasone exposure significantly suppressed hemolytic complement activity in bacteria-infected fish. These results clearly indicate that exposure to a high concentration of dexamethasone suppressed the carp immune system and caused subsequent mortality. Thus, this proposed test method is likely to be useful for evaluating the immunomodulatory effects of chemicals in fish. (C) 2016 Elsevier Ltd. All rights reserved.
  • Shin-Ichi Kitamura, Masaki Akizuki, Jun-Young Song, Kei Nakayama
    MARINE POLLUTION BULLETIN 124 (2) 835 - 838 0025-326X 2017/11 [Peer-reviewed]
     Scientific journal 
    We investigated the effect of combined exposure to nodavirus infection and TBT on medaka (Oryzias latipes). Medaka larvae were infected by immersion in medium containing nodavirus at titers of 10(2.5),10(3.5), or 10(4.5) TCID50/mL Infected fish then were exposed to TBT at 0, 0.17, 0.52,1.6, or 4.7 mu g/L. Of the 12 groups exposed to both stressors, the mortalities of 6 (10(2.5) TCID50/mL + 0.52, 1.6, or 4.7 mu g/L, 10(3.5) TCID50/mL + 4.7 mu g/L and 10(4.5) TCID50/mL + 1.6 or 4.7 mu g/L) were significantly higher than that of each TBT control. Specifically, mortality was 46 +/- 5.5% in the group exposed to both 10(2.5) TCID50/mL virus and 0.52 mu g/LTBT, which represent the lowest observed effective dose and concentration, respectively, among the 6 groups with increased mortalities. Our results suggest that combined exposure to both stressors suppresses antiviral mechanisms in the fish, thus increasing mortality. (C) 2017 Elsevier Ltd. All rights reserved.
  • Tatsuya Itoyama, Moe Kawara, Makiko Fukui, Yuki Sugahara, Daisuke Kurokawa, Masahumi Kawaguchi, Shin-Ichi Kitamura, Kei Nakayama, Yasunori Murakami
    MARINE POLLUTION BULLETIN 124 (2) 792 - 797 0025-326X 2017/11 [Peer-reviewed]
     Scientific journal 
    Pyrene, a member of the polycyclic aromatic hydrocarbons (PAHs), contributes to abnormality in the size of the brain and the swimming behavior of pufferfish (Takifugu niphobles) larvae. We hypothesized that the aryl hydrocarbon receptor (AHR) may mediate pyrene-induced toxic effects because AHR is assumed to be a candidate for the downstream target of PAHs in many cases. To identify the contribution of AHR on developing pufferfish, we performed exposure experiments using P-naphthoflavone, an agonist of AHR We found that the toxic effects of pyrene and p-naphthoflavone in pufferfish larvae are fundamentally different. Pyrene specifically induced problems in the developing midbrain and in swimming behavior, while p-naphthoflavone affected the heartbeat rate and the size of the yolk. These results suggest that the behavioral and morphological abnormality caused by pyrene exposure is mediated by an AHR-independent pathway. Alternatively, defects caused by pyrene may be attributed to the inhibition of the FGF signal. (C) 2017 Elsevier Ltd. All rights reserved.
  • Thi Lan Thanh Bien, Ngo Vy Thao, Shin-Ichi Kitamura, Yumiko Obayashi, Satoru Suzuki
    MICROBES AND ENVIRONMENTS 32 (2) 174 - 179 1342-6311 2017/06 [Peer-reviewed]
     Scientific journal 
    Extracellular DNA (exDNA) is released from bacterial cells through various processes. The antibiotic resistance genes (ARGs) coded on exDNA may be horizontally transferred among bacterial communities by natural transformation. We quantitated the released/leaked tetracycline resistance gene, tet(M) over time under grazing stress by ciliates and heterotrophic nanoflagellates (HNFs), and found that extracellular tet(M) (ex-tetM) increased with bacterial grazing. Separate microcosms containing tet(M)-possessing bacteria with ciliates or HNFs were prepared. The copy number of ex-tetM in seawater in the ciliate microcosm rapidly increased until 3 d after the incubation, whereas that in the HNF microcosm showed a slower increase until 20 d. The copy number of ex-tetM was stable in both cases throughout the incubation period, suggesting that extracellular ARGs are preserved in the environment, even in the presence of grazers. Additionally, ARGs in bacterial cells were constant in the presence of grazers. These results suggest that ARGs are not rapidly extinguished in a marine environment under grazing stress.
  • Nakayama, Kei, Sato, Kentaro, Shibano, Takazumi, Isobe, Tomohiko, Suzuki, Go, Kitamura, Shin-Ichi
    Environmental Toxicology and Chemistry 35 (4) 946 - 952 0730-7268 2016 [Peer-reviewed]
     Scientific journal
  • M. Habibur Rahman, Kentaro Q. Sakamoto, Shin-Ichi Kitamura, Lisa Nonaka, Satoru Suzuki
    POLAR BIOLOGY 38 (10) 1775 - 1781 0722-4060 2015/10 [Peer-reviewed]
     Scientific journal 
    Antibiotic-resistant bacteria can be detected in pristine environments and animals. Tetracycline (TC) is frequently used for wide areas of veterinary medicine, which selects TC-resistant bacteria. The TC resistance genes are known from natural environments, and tet(M) is the broadest host range tet gene. Here, we report that TC-resistant bacteria and the TC resistance gene tet(M) were diverse in Ad,lie penguin intestines, even within a single penguin colony. Total bacterial counts were as high as 10(7) CFU g(-1), and TC-resistant bacteria ranged from 1.4 x 10(2) to 6.6 x 10(3) CFU g(-1) intestinal contents, which was 0-0.54 % of the total viable count. Phylogenetic affiliation of TC-resistant bacteria revealed a variety of Gram-positive and Gram-negative bacteria. The tet(M) gene was identified in 32.3 % of TC-resistant strains, and two tet(M) genotypes were identified within one penguin colony, suggesting various contamination origins of tet(M).
  • Satoshi Kimura, Kei Nakayama, Masahisa Wada, Ung-Jin Kim, Kaoru Azumi, Takao Ojima, Akino Nozawa, Shin-Ichi Kitamura, Euichi Hirose
    DISEASES OF AQUATIC ORGANISMS 116 (2) 143 - 148 0177-5103 2015/10 [Peer-reviewed]
     Scientific journal 
    Soft tunic syndrome is a fatal disease in the edible ascidian Halocynthia roretzi, causing serious damage to ascidian aquaculture in Korea and Japan. In diseased individuals, the tunic, an integumentary extracellular matrix of ascidians, softens and eventually tears. This is an infectious disease caused by the kinetoplastid flagellate Azumiobodo hoyamushi. However, the mechanism of tunic softening remains unknown. Because cellulose fibrils are the main component of the tunic, we compared the contents and structures of cellulose in healthy and diseased tunics by means of biochemical quantification and X-ray diffractometry. Unexpectedly, the cellulose contents and structures of cellulose microfibrils were almost the same regardless of the presence or absence of the disease. Therefore, it is unlikely that thinning of the microfibrils occurred in the softened tunic, because digestion should have resulted in decreases in crystallinity index and crystallite size. Moreover, cellulase was not detected in pure cultures of A. hoyamushi in biochemical and expressed sequence tag analyses. These results indicate that cellulose degradation does not occur in the softened tunic.
  • Akatsuki Nawata, Euichi Hirose, Shin-Ichi Kitamura, Akira Kumagai
    DISEASES OF AQUATIC ORGANISMS 115 (3) 253 - 262 0177-5103 2015/08 [Peer-reviewed]
     Scientific journal 
    Soft tunic syndrome in the edible ascidian Halocynthia roretzi is caused by the kineto plastid flagellate Azumiobodo hoyamushi, which was found to assume a fusiform cell form with 2 flagella in axenic, pure culture. When the flagellate form was incubated in sterilized artificial seawater (pH 8.4), some of the cells became cyst-like and adhered to the bottom of the culture plate. The cyst-like forms were spherical or cuboidal, and each had 2 flagella encapsulated in its cytoplasm. Encystment was also induced in culture medium alkalified to the pH of seawater (8.4) but not in unmodified (pH 7.2) or acidified media (pH 6.4). More than 95% of the cyst-like cells converted to the flagellate form within 1 d following transfer to seawater containing ascidian tunic extracts from host ascidians. The cyst-like cells were able to survive in seawater with no added nutrients for up to 2 wk at 20 degrees C and for a few months at 5 to 15 degrees C. The survival period in seawater depended on temperature: some cyst-like cells survived 3 mo at 10 degrees C, and ca. 95% of these converted to flagellate forms in seawater containing tunic extracts. Thus, A. hoyamushi is able to persist under adverse conditions in a cyst-like form able to adhere to organic and inorganic substrata for protracted periods of time.
  • Ngo Vy Thao, Akino Nozawa, Yumiko Obayashi, Shin-Ichi Kitamura, Taichi Yokokawa, Satoru Suzuki
    MARINE ENVIRONMENTAL RESEARCH 109 95 - 102 0141-1136 2015/08 [Peer-reviewed]
     Scientific journal 
    The biodegradation of proteins in seawater requires various proteases which are commonly thought to be mainly derived from heterotrophic bacteria. We, however, found that protists showed a high protease activity and continuously produced trypsin-type enzymes. The free-living marine heterotrophic ciliate Paranophrys marina together with an associated bacterium was isolated and used for microcosm incubation with different concentrations of killed bacteria as food for 10 days. The results showed that the coexistence of the ciliate with its associated bacterium produced a significant protease activity in both cell-associated and cell-free fractions while that in the associated bacterium only microcosm was negligible. The protease profiles are different between cell-associated and cell-free fractions, and a trypsin-type enzyme hydrolyzing Boc-Val-Leu-Lys-MCA was detected throughout the period in the presence of ciliates. This suggests that ciliates release proteases into the surrounding environment which could play a role in protein digestion outside cells. It has been previously suggested that bacteria are the major transformers in seawater. We here present additional data which indicates that protists, or at least ciliates with their specific enzymes, are a potential player in organic matter degradation in water columns. (C) 2015 Elsevier Ltd. All rights reserved.
  • Kei Nakayama, Yoshiyuki Inoue, Naomi Ikeda, Naoki Hashizume, Hidekazu Murakami, Takeshi Ishibashi, Hirofumi Ikeda, Tomohiko Isobe, Shin-Ichi Kitamura, Go Suzuki
    MARINE POLLUTION BULLETIN 85 (2) 370 - 375 0025-326X 2014/08 [Peer-reviewed]
     Scientific journal 
    Uptake and biological effects of synthetic glucocorticoids (GCs) were analyzed using common carp (Cyprinus carpio). Fish were exposed to clobetasol propionate (CP) or clobetasone butyrate (CB) individually or in mixture at 1 mu g L-1 for 21 days. Bioconcentration factor (BCF) of CB was calculated as 100, and BCF of CP was less than 16. No effects were found in fish erythrocyte and leukocyte numbers and serum glucose levels after exposure to the selected GCs. On the other hand, serum concentrations of free amino acids significantly increased in GC-exposed groups. Thus, exposures to synthetic GCs at relatively low concentrations seemed to cause enhancement of protein degradation and subsequent increase of serum free amino acids without a corresponding increase in serum glucose levels, an effect which might be related to partial induction of gluconeogenesis by GC. (C) 2014 Elsevier Ltd. All rights reserved.
  • Yuki Sugahara, Masahumi Kawaguchi, Tatsuya Itoyama, Daisuke Kurokawa, Yasuhiko Tosa, Shin-Ichi Kitamura, Itsuki C. Handoh, Kei Nakayama, Yasunori Murakami
    MARINE POLLUTION BULLETIN 85 (2) 479 - 486 0025-326X 2014/08 [Peer-reviewed]
     Scientific journal 
    Spills of heavy oil (HO) have an adverse effect on marine life. We have demonstrated previously that exposure to HO by fertilized eggs of the pufferfish (Takifugu rubripes) induces neural disruption and behavioral abnormality in early-hatched larvae. Here, two kinds of polycyclic aromatic hydrocarbons, pyrene and phenanthrene, were selected to examine their toxic effects on larval behavior of another pufferfish species (T. niphobles). Larvae exposed to pyrene or phenanthrene exhibited no abnormalities in morphology. However, those exposed to pyrene but not phenanthrene swam in an uncoordinated manner, although their swimming distance and speed were normal. The optic tectum, a part of the midbrain, of pyrene-exposed larvae did not grow to full size. Thus, these findings are indicated that pyrene might be a contributor to the behavioral and neuro-developmental toxicity, although there is no indication that it is the only compound participating in the toxicity of the heavy oil mixture. (C) 2014 Elsevier Ltd. All rights reserved.
  • Euichi Hirose, Akira Kumagai, Akatsuki Nawata, Shin-Ichi Kitamura
    DISEASES OF AQUATIC ORGANISMS 109 (3) 251 - 256 0177-5103 2014/07 [Peer-reviewed]
     Scientific journal 
    The infectious kinetoplastid Azumiobodo hoyamushi causes 'soft tunic syndrome', a serious problem in aquaculture of the edible ascidian Halocynthia roretzi. Infection tests using diseased tunics demonstrated that juvenile (0.8 yr old) individuals never developed soft tunic syndrome, but all individuals in the other age groups (1.8, 2.8, and 3.8 yr old) showed the disease symptoms. In the infection tests, tunic softening was first observed at the tunic around siphons. Based on ultrastructural observation of the inner wall of the branchial siphon, the tunic lining the inner wall in juveniles (0.5 yr old) was completely covered with cuticle, which had a dense structure to prevent bacterial and protist invasion. In contrast, the tunic was often partly damaged and not covered with cuticle in healthy adults (>= 2.5 yr old). The damaged tunic in the siphon wall could be an entrance for A. hoyamushi into the tunic of adult hosts.
  • Shogo Iwakiri, Jun-Young Song, Kei Nakayama, Myung-Joo Oh, Minoru Ishida, Shin-Ichi Kitamura
    FISH & SHELLFISH IMMUNOLOGY 38 (2) 406 - 411 1050-4648 2014/06 [Peer-reviewed]
     Scientific journal 
    Lymphocystis disease virus (LCDV) is the causative agent of lymphocystis disease (LCD). In this study, we investigated the mechanisms of lymphocystis cell (LCC) formation from the viewpoint of gene expression changes in the infected fish. LCC occurrence and virus titers in the experimentally infected Japanese flounder, Paralichthys olivaceus were monitored by visual confirmation and real-time PCR, respectively. The gene expression changes in the fish fin were investigated by microarray experiments. LCCs firstly appeared in the fish at 21 days post infection (dpi). LCD incidence increased with time and reached 92.9% at 62 dpi. LCDV genome was firstly detected from dorsal fins at 14 dpi, and the relative amount of the genome gradually-increased until 56 dpi. Since the occurrence of LCC was approximately synchronized with increasing of the virus genome, virus replication might play important roles for LCC formation. The microarray detected a few gene expression changes until 28 dpi. However, the number of expression changed genes dramatically increased between 28 and 42 dpi in which LCCs formation was active. From the microarray data analyses, apoptosis and cell division related genes were down-regulated, whereas cell fusion and collagen related genes were up-regulated at 42 dpi. Together with the observation of morphological changes of LCCs in previous reports, it is suggested that the following steps are involved in LCC formation: the virus infected cells were (1) inhibited apoptotic death and (2) cell division before enlargement, (3) hypertrophied by cell fusion, and (4) surrounded by a hyaline capsule associated with the alteration of collagen fibers. (C) 2014 Elsevier Ltd. All rights reserved.
  • Andreia Cruz, Nuno Micaelo, Vitor Felix, Jun-Young Song, Shin-Ichi Kitamura, Satoru Suzuki, Sonia Mendo
    JOURNAL OF GENERAL AND APPLIED MICROBIOLOGY 59 (1) 39 - 47 0022-1260 2013 [Peer-reviewed]
     Scientific journal 
    The mechanism of bacterial resistance to tributyltin (TBT) is still unclear. The results herein presented contribute to clarify that mechanism in the TBT-resistant bacterium Aeromonas molluscorum Av27. We have identified and cloned a new gene that is involved in TBT resistance in this strain. The gene is highly homologous (84%) to the Aeromonas hydrophila-sugE gene belonging to the small multidrug resistance gene family (SMR), which includes genes involved in the transport of lipophilic drugs. In Av27, expression of the Av27-sugE was observed at the early logarithmic growth phase in the presence of a high TBT concentration (500 mu M), thus suggesting the contribution of this gene for TBT resistance. E. coli cells transformed with Av27-sugE become resistant to ethidium bromide (EtBr), chloramphenicol (CP) and tetracycline (TE), besides TBT. According to the Moriguchi logP (miLogP) values, EtBr, CP and TE have similar properties and are substrates for the sugE-efflux system. Despite the different miLogP of TBT, E. coli cells transformed with Av27-sugE become resistant to this compound. So it seems that TBT is also a substrate for the SugE protein. The modelling studies performed also support this hypothesis. The data herein presented clearly indicate that sugE is involved in TBT resistance of this bacterium.
  • Tadashi Isshiki, Takeya Morimoto, Masahiro Iwasaki, Masaaki Abe, Taizou Nagano, Takashi Hazama, Jun-Young Song, Shin-Ichi Kitamura
    FISH PATHOLOGY 47 (4) 121 - 128 0388-788X 2012/12 [Peer-reviewed]
     Scientific journal 
    We examined the effectiveness of a formalin-inactivated vaccine against viral hemorrhagic septicemia (VHS) in Japanese flounder Paralichthys olivaceus by the pathogen challenge. Japanese flounder (average weight, 10 g) kept at 12 degrees C, 20 degrees C and 28 degrees C were vaccinated by intraperitoneal injection of a formalin-inactivated VHS virus (VHSV) and maintained at each temperature for 21, 19 and 17 days post vaccination (dpv), respectively. The fish vaccinated at 20 degrees C and 28 degrees C were acclimated to 12 degrees C, and then all vaccinated fish were challenged with VHSV at 12 degrees C at 21 dpv. Fish that received the vaccine at 20 degrees C showed relative percent survival (RPS) of 48%, compared with 0% for those given the vaccine at 12 degrees C and 28 degrees C. In other experiment, efficient protection against VHSV lasted at least 7 mo in Japanese flounder (average weight, 100 g) vaccinated at 20 degrees C and maintained at ambient temperature, where high RPS values (71-100%) were obtained after viral challenges at 18, 77, 98 and 213 dpv. We obtained promising results that a single immunization with the formalin-inactivated vaccine at the physiologically optimal temperature (20 degrees C) provided significant protective and long-lasting immunity to Japanese flounder against VHS.
  • Masahumi Kawaguchi, Yuki Sugahara, Tomoe Watanabe, Kouta Irie, Minoru Ishida, Daisuke Kurokawa, Shin-Ichi Kitamura, Hiromi Takata, Itsuki C. Handoh, Kei Nakayama, Yasunori Murakami
    ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH 19 (7) 2488 - 2497 0944-1344 2012/08 [Peer-reviewed]
     Scientific journal 
    Spills of heavy oil (HO) over the oceans have been proven to have an adverse effect on marine life. It has been hypothesized that exposure of early larvae of sinking eggs to HO leads largely to normal morphology, whereas abnormal organization of the developing neural scaffold is likely to be found. HO-induced disruption of the nervous system, which controls animal behavior, may in turn cause abnormalities in the swimming behavior of hatched larvae. To clarify the toxicological effects of HO, we performed exposure experiments and morphological and behavioral analyses in pufferfish (Takifugu rubripes) larvae. Fertilized eggs of pufferfish were exposed to 50 mg/L of HO for 8 days and transferred to fresh seawater before hatching. The hatched larvae were observed for their swimming behavior, morphological appearance, and construction of muscles and nervous system. In HO-exposed larvae, we did not detect any anomaly of body morphology. However, they showed an abnormal swimming pattern and disorganized midbrain, a higher center controlling movement. Our results suggest that HO-exposed fishes suffer developmental disorder of the brain that triggers an abnormal swimming behavior and that HO may be selectively toxic to the brain and cause physical disability throughout the life span of these fishes.
  • Jun-Young Song, Sho Ohta, Kei Nakayama, Yasunori Murakami, Shin-Ichi Kitamura
    ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH 19 (6) 2300 - 2304 0944-1344 2012/07 [Peer-reviewed]
     Scientific journal 
    The immunotoxicities of oil and its components on fish immunities have been investigated, but there is little literature on the recovery of the fish from the immune suppression. Therefore, the recovery of Japanese flounder Paralichthys olivaceus from an immunosuppressive effect due to heavy oil (HO) exposure was investigated in this study. Fish were exposed to HO at a concentration of 0.385 g/L for 2 days, while control fish received no exposure. Seven fish were sampled at 0, 3, 7, and 14 days post-exposure. The respiratory rate was measured everyday as an indicator of the acute effect of HO exposure. Fish serum was collected and used for antibacterial activity assay against Edwardsiella tarda. Expression changes of respiratory and immune-related genes were evaluated by real-time PCR. The respiratory rate was significantly increased in the HO-exposed group until 4 days post-exposure. A respiratory-related gene, beta-hemoglobin, was also significantly downregulated in the spleen both at 0 and 7 days post-exposure and kidney at 3 days post-exposure in HO-exposed fish. Immunotoxicity, including suppression of antibacterial activities and downregulation of the IgM gene, was observed in HO-exposed fish until 3 days post-exposure, but not after that time. From these results, we conclude that the fish likely return to normal status around 1 week.
  • Jun-Young Song, Kei Nakayama, Emiko Kokushi, Kazuki Ito, Seiichi Uno, Jiro Koyama, M. Habibur Rahman, Yasunori Murakami, Shin-Ichi Kitamura
    ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 31 (4) 828 - 835 0730-7268 2012/04 [Peer-reviewed]
     Scientific journal 
    Heavy oil (HO) pollution is one of the most important environmental issues globally. However, little is known about the immunotoxicity of HO in fish. We therefore investigated the effects of HO exposure on immunocompetence and expression of immune-related genes in Japanese flounder, Paralichthys olivaceus. To test immunocompetency, serum collected from the fish was mixed with Edwardsiella tarda, plated, and the resultant numbers of bacterial colonies were counted. Plates with serum from HO-exposed fish (5 d postexposure [dpe]) had significantly higher numbers of colonies than those of the untreated control group, suggesting that HO exposure suppresses immunocompetency. Downregulation of the immunoglobulin light chain (IgM) gene in HO-exposed fish at 5 dpe was detected by real-time polymerase chain reaction. These results suggest that IgM-mediated immunity is suppressed by HO exposure. We measured polycyclic aromatic hydrocarbon (PAH) concentrations in the liver of the fish. Low molecular weight PAHs were found to be taken up at high concentrations in fish liver; therefore, they are likely the cause of immune suppression in the fish. Environ. Toxicol. Chem. 2012;31:828835. (c) 2012 SETAC
  • Euichi Hirose, Akino Nozawa, Akira Kumagai, Shin-Ichi Kitamura
    DISEASES OF AQUATIC ORGANISMS 97 (3) 227 - 235 0177-5103 2012/01 [Peer-reviewed]
     Scientific journal 
    We used morphological and genetic analyses to investigate a pathogenic kinetoplastid isolated from a diseased edible ascidian Halocynthia roretzi with soft tunic syndrome. The morphological characteristics of the kinetoplastid are similar to those in the order Neobodonida in the subclass Metakinetoplastida. However, the presence of unique globular bodies distinguishes this kinetoplastid from the other polykinetoplastic genera (i.e. Cruzella, Dimastigella and Rhynchobodo) in this order. These globular bodies are cytoplasmic inclusions without an outer delimiting membrane and are composed of a homologous granular matrix containing electron-dense bands. A phylogenetic tree based on 18S rRNA gene sequences also indicated that the kinetoplastid belongs to the order Neobodonida, although it forms an independent clade in this order. From these results, we propose a new genus in the order Neobodonida, i.e. Azumiobodo gen. nov., and Azumiobodo hoyamushi as the type species for the genus.
  • Akira Kumagai, Atsushi Suto, Hiroshi Ito, Toru Tanabe, Jun-Young Song, Shin-Ichi Kitamura, Euichi Hirose, Takashi Kamaishi, Satoshi Miwa
    DISEASES OF AQUATIC ORGANISMS 95 (2) 153 - 161 0177-5103 2011/06 [Peer-reviewed]
     Scientific journal 
    An etiological study was conducted to clarify whether the flagellate-like cells found in histological preparations of the tunic of diseased Halocynthia roretzi (Drasche) were the causative agent of soft tunic syndrome in this ascidian. When pieces of softened diseased tunic were incubated overnight in sterile seawater, live flagellated cells, which were actively swimming in the seawater, were observed in 47 out of 61 diseased ascidians (77%), but not in moribund or abnormal individuals with normal tunics (n = 36) nor in healthy animals (n = 19). The flagellate was morphologically very similar to those observed in histological sections of the diseased tunic. By contrast, flagellates were not found in tunic pieces of healthy, moribund, and abnormal individuals that did not exhibit softening of the tunic. Light and electron microscopy revealed that the flagellate has polykinetoplastic mitochondria with discoidal cristae. The cytomorphologies of the flagellate were the same as those of the flagellate-like cells in the diseased tunic. We cultured the flagellate from the softened tunic in vitro and confirmed that the tunics of healthy ascidians, which were immersion-challenged with suspensions of the subcultured flagellates, became softened 17 d after exposure, including the final 12 d in aerated, running seawater. The occurrence of flagellates was also confirmed by incubating pieces of soft tunic from experimentally infected animals in seawater overnight. These results indicate that the flagellate is the causative agent of soft tunic syndrome.
  • Sung-Ju Jung, Eun-Young Im, Michaela C. Strueder-Kypke, Shin-Ichi Kitamura, Patrick T. K. Woo
    PARASITOLOGY RESEARCH 108 (5) 1153 - 1161 0932-0113 2011/05 [Peer-reviewed]
     Scientific journal 
    The scuticociliate Miamiensis avidus is a histophagous parasite that causes high mortality in cultured marine fishes. Small subunit ribosomal RNA (SSU rRNA) and mitochondrial cytochrome c oxidase subunit 1 (cox1) genes were analyzed for 21 strains of M. avidus isolated from diseased olive flounder (Paralichthys olivaceus), ridged-eye flounder (Pleuronichthys cornutus), and spotted knifejaw (Oplegnathus fasciatus) in Korea and Japan (collected in 2003-2007). Analysis of SSU rRNA gene sequences (1,759 bp) indicates they are very conserved with less than 0.17% (3 nucleotides) differences suggesting that SSU rRNA are useful to identify M. avidus; however, the cox1 gene (900 bp) has higher variations with intraspecific divergences up to 5.67% (51 nucleotides). A distance tree of cox1 gene sequences based on a neighbor-joining analysis can separate 21 strains into five cox1 types (two heterogeneous clusters and three individual branches). The cox1-type matches with serotype of strains but do not reflect geographical origins, host species, or pathogenicity.
    J. Toxicol. Sci. 36 (4) 487 - 491 0388-1350 2011
  • Jun-Young Song, Kei Nakayama, Yasunori Murakami, Shin-Ichi Kitamura
    MARINE POLLUTION BULLETIN 63 (5-12) 362 - 365 0025-326X 2011 [Peer-reviewed]
     Scientific journal 
    The relationship between chemical exposure and disease outbreak in fish has not been fully defined due to the limitations of experimental systems (model fish and pathogens). Therefore, we constructed a system using the Japanese flounder, Paralichthys olivaceus, and viral haemorrhagic septicemia virus (VHSV), and evaluated it by heavy oil (HO) exposure. The fish were exposed to HO at 0.3, 0.03, 0.003, and 0 g/L following VHSV infection at doses of 10(2.5) or 10(3.5) tissue culture infectious dose (TCID)(50)/fish. As a result, groups given the dual stressors showed more than 90% mortality. Although VHSV infection at 10(2.5) and 10(3.5) TCID50/fish without HO exposure also induced high mortality, at 68.8% and 81.3%, respectively, HO exposure induced faster and higher mortality in the virus carrier fish, indicating that chemical stressors raise the risk of disease outbreak in fish. The experimental system established in this study could be useful for chemical risk assessment. (C) 2011 Elsevier Ltd. All rights reserved.
  • Masahumi Kawaguchi, Jun-Young Song, Kouta Irie, Yasunori Murakami, Kei Nakayama, Shin-Ichi Kitamura
    MARINE POLLUTION BULLETIN 63 (5-12) 356 - 361 0025-326X 2011 [Peer-reviewed]
     Scientific journal 
    It has been well known that oil spills cause serious problems in the aquatic organisms. In particular, some species of teleosts, which develop on the sea surface thought to be affected by heavy oil (HO). During the embryogenesis, the nervous system is constructed. Therefore, it is important to study the toxicological effects of HO on the developing neurons. We exposed HO to eggs of Japanese flounder (Paralichthys olivaceus) and investigated the neural disorder. In larvae exposed by HO at the concentration of 8.75 mg/L, the facial and lateral line nerves partially entered into the incorrect region and the bundle was defasciculated. Furthermore, in the HO-exposed larvae, Sema3A, a kind of axon guidance molecule, was broadly expressed in second pharyngeal arch, a target region of facial nerve. Taken together, we suggested the possibility that the abnormal expression of Sema3A affected by HO exposure causes disruption of facial nerve scaffolding. (C) 2011 Elsevier Ltd. All rights reserved.
  • Kouta Irie, Masahumi Kawaguchi, Kaori Mizuno, Jun-Young Song, Kei Nakayama, Shin-Ichi Kitamura, Yasunori Murakami
    MARINE POLLUTION BULLETIN 63 (5-12) 297 - 302 0025-326X 2011 [Peer-reviewed]
     Scientific journal 
    Heavy oil (HO) on the sea surface penetrates into fish eggs and prevents the normal morphogenesis. To identify the toxicological effects of HO in the context of the egg types, we performed exposure experiments using floating eggs and sinking eggs. In the course of development, HO-exposed embryos of floating eggs showed abnormal morphology, whereas early larva of the sinking eggs had almost normal morphology. However, the developing peripheral nervous system of sinking eggs showed abnormal projections. These findings suggest that HO exposed fishes have problems in the developing neurons, although they have no morphological malformations. Through these observations, we conclude that HO is strongly toxic to floating eggs in the morphogenesis, and also affect the neuron development in both floating and sinking eggs. (C) 2011 Elsevier Ltd. All rights reserved.
  • Kei Nakayama, Itsuki C. Handoh, Shin-Ichi Kitamura, Eun-Young Kim, Hisato Iwata, Shinsuke Tanabe
    SCIENCE OF THE TOTAL ENVIRONMENT 408 (23) 5824 - 5827 0048-9697 2010/11 Scientific journal 
    Here we propose a novel microarray data analysis method applicable to evaluation of the chemical effects on wild animals First, we analyzed correlations between log-transformed hepatic 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalent (TEQ) levels and probe signals detected in wild cormorant liver to screen contaminant-responsive genes Second, principal component analysis (PCA) was conducted using the screened probes Third, these probes were divided into two groups based on our PCA result Finally, we calculated Euclidian distance of signals, which is equivalent to variance of gene expressions, in each probe set, and analyzed the relationship between log-transformed hepatic TEQ levels and Euclidian distances A probe set whereby the calculated Euclidian distance was positively correlated with TEQ levels, could indicate genes that were directly affected by dioxins or other persistent organic pollutants (POPs), hence they can be used as biomarkers By contrast, there were a number of probes whereby the Euclidian distance was negatively correlated with TEQ levels In the latter probe group, the smaller Euclidian distances in highly contaminated individuals could point to changes in physiological activities of wild cormorants Therefore, our microarray data analysis method will provide new insights into POPs-responsive genes in field-collected samples for toxicogenomics studies (C) 2010 Elsevier BV All rights reserved
  • Nahoko Tange, Jun-Young Song, Shin-Ichi Kitamura
    FISH PATHOLOGY 45 (3) 130 - 132 0388-788X 2010/09 [Peer-reviewed]
     Scientific journal 
    We designed a PCR primer set for specific detection of Miamiensis avidus causing scuticociliatosis in Japanese flounder Paralichthys olivaceus. In the PCR targeting the small subunit ribosomal RNA gene of M. avidus, the expected PCR product with 1,433 bp was amplified from four isolates of M. avidus including three different serotypes, but not from other scuticociliates including Pseudocohnilembus persalinus, P hargisi and Uronema marinum. Detection limit of the present PCR was 125 fg of genomic DNA. When a group of Japanese flounder suffering the disease was examined by the PCR, 90% of symptomatic fish and 50% of asymptomatic fish were found positive. Thus it is considered that the PCR is useful for detection and identification of M. avidus and consequently for diagnosis of scuticociliatosis in Japanese flounder.
  • S-I Kitamura, S-I Ohtake, J-Y Song, S-J Jung, M-J Oh, B-D Choi, K. Azumi, E. Hirose
    JOURNAL OF FISH DISEASES 33 (2) 153 - 160 0140-7775 2010/02 Scientific journal 
    'Soft tunic syndrome' causes mass mortality in the edible ascidian Halocynthia roretzi in Korean and Japanese aquaculture. In histopathological comparison, there were no specific differences between diseased specimens from Korea and Japan, indicating that soft tunic syndrome occurring in Korea and Japan is the same disease. No bacterial or protozoan cells were microscopically detected in either healthy or diseased tunics suggesting they are not the direct causes of soft tunic syndrome. Attempts were made to isolate virus from affected ascidians taking into account temperature conditions in which soft tunic syndrome is most prevalent in the field. However, no viruses were isolated from diseased or non-diseased specimens using chinook salmon embryo (CHSE-214), flounder fin (FFN) or epithelioma papillosum cyprini (EPC) cell lines.
  • J-Y Song, K. Sasaki, T. Okada, M. Sakashita, H. Kawakami, S. Matsuoka, H-S Kang, K. Nakayama, S-J Jung, M-J Oh, S-I Kitamura
    JOURNAL OF FISH DISEASES 32 (12) 1027 - 1034 0140-7775 2009/12 Scientific journal 
    In Japan and Korea, outbreaks of scuticociliatosis have frequently occurred in Japanese flounder, Paralichthys olivaceus. Morphological observations and small subunit rRNA gene sequences have shown that the causative agent of scuticociliatosis in the flounder is Miamiensis avidus (syn. Philasterides dicentrarchi). In this study, we elucidated the antigenic differences between six Japanese M. avidus isolates as an initial step toward developing an effective vaccine against the disease. Four Japanese flounder isolates (IyoI, Nakajima, JF05To and Mie0301 isolates), one spotted knifejaw, Oplegnathus punctatus, isolate (SK05Kyo), and one ridged-eye flounder, Pleuronichthys cornutus, isolate (RF05To) were subjected to serological analysis. Antisera against IyoI, SK05Kyo, Nakajima and Mie0301 isolates were raised in rabbits and used for immobilization assays and Western blotting. Immobilization assays showed that the six isolates could be divided into three groups, tentatively designated serotype I for IyoI, JF05To, RF05To, SK05Kyo, serotype II for Nakajima and serotype III for Mie0301. Western blotting results supported these three serotypes, with marked similarities in the banding profiles of IyoI, JF05To, RF05To and SK05Kyo isolates, which were distinct from the Nakajima and Mie0301 isolates. Three isolates, IyoI, Nakajima and Mie0301 that were selected as representatives of each serotype, were highly pathogenic to Japanese flounder by experimental infection. Based on these findings, we propose that there are at least three M. avidus serotypes in Japan.
  • Wi-Sik Kim, Seok-Ryel Kim, Duwoon Kim, Jong-Oh Kim, Myoung-Ae Park, Shin-Ichi Kitamura, Heung-Yun Kim, Do-Hyung Kim, Hyun-Ja Han, Sung-Ju Jung, Myung-Joo Oh
    AQUACULTURE 296 (1-2) 165 - 168 0044-8486 2009/11 Scientific journal 
    We examined the cause of a disease outbreak in juvenile and market-sized olive flounder Paralichthys olivaceus from aquaculture farms in the south sea of Korea in 2005. Principal signs included expanded abdomen, congested liver and enlarged spleen and kidney, with fish suffering heavy mortality (40 to 60%). Although no parasites or bacteria were isolated from diseased fish, tissue filtrates still produced cytopathic effects (CPE) in FHM, CHSE-214 and FSP cells. PCR reactions of tissue filtrates from diseased fish and supernatants of cell cultures showing CPE indicated specific 587 bp fragments from the glycoprotein (G) gene of the viral hemorrhagic septicemia virus (VHSV). Supporting this, the nucleotide sequences among three isolates had shown 100% homology, and 99.3% and 99.8% homology with the VHSV JY-0112 isolate from flounder in Korea and VHSV obama25 isolate from flounder in Japan, respectively. Experimental infection trials using supernatants of cell cultures showing CPE gave cumulative mortalities of 100% and 60% for virus-injected and virus-immersed flounder, respectively. The pathological signs shown were generally similar to those of naturally diseased fish. Results of this investigation indicate that VHSV was the causative agent of the natural epizootic. (C) 2009 Elsevier B.V. All rights reserved.
  • M. Hossain, S-R Kim, S-I Kitamura, D-W Kim, S-J Jung, T. Nishizawa, M. Yoshimizu, M-J Oh
    JOURNAL OF FISH DISEASES 32 (8) 699 - 703 0140-7775 2009/08 Scientific journal 
    Olive flounder artificially infected with lymphocystis disease virus (LCDV) were reared at 10, 20 and 30 degrees C for 60 days, to compare LCD-incidence. In the fish reared at 20 degrees C, lymphocystis cells appeared on the skin and fins at 35 days post-challenge, and the cumulative LCD-incidence was 80% at 60 days. High levels of LCDV, with a mean polymerase chain reaction (PCR) titre of 10(6) PCR-U mg(-1) tissue, were detected in the fins and skin of LCD-affected fish at 20 degrees C, but were not detected in the spleen, kidney, brain and intestinal tissues of these fish. No LCD clinical signs were observed in the fish reared at 10 degrees C and 30 degrees C; however, a low level of LCDV (10(3) PCR-U mg(-1) tissue) was detected in the fins and skin of these fish. By increasing the rearing temperature from 10 to 20 degrees C, lymphocystis clusters appeared on the skin and fins of the fish with no previous LCD clinical signs within 33 days after the temperature change. It was shown that permissive cells for LCDV infection exist in the epidermis of olive flounder. At low temperatures, small amounts of LCDV were able to persist over a period extended for a further 45 days in the fish epidermis, even though the fish showed no LCD clinical signs. The optimum growth temperature of LCDV is near 20 degrees C.
  • Jun-Young Song, Shin-Ichi Kitamura, Myung-Joo Oh, Hyun-Sil Kang, Je-Hee Lee, Shin-Ji Tanaka, Sung-Ju Jung
    DISEASES OF AQUATIC ORGANISMS 83 (2) 133 - 143 0177-5103 2009/02 Scientific journal 
    The scuticociliates Miamiensis avidus (syn. Philasterides dicentrarchi), Pseudocohnilembus persalinus, Pseudocohnilembus hargisi and Uronema marinum were cloned and identified using morphological characteristics and the small subunit ribosomal RNA gene (SSU rRNA). M. avidus strains YS1, WS1, YK1 and JJ3 from southern coastal areas and Jeju Island in Korea were pathogenic to olive flounder Paralichthys olivaceus (80 to 100% mortality in 8 to 10 g fish) when inoculated intraperitoneally (i.p.) with 1.0 to 1.4 x 10(6) ciliates fish(-1). Mortality was lower (10 to 45 %) when the inoculum was 1.0 to 1.4 x 10(4) ciliates fish(-1) in the i.p.-injected group. The M avidus strains of YS1, WS1, YK1 and JJ3 caused 60 to 100% mortality by immersion infection with 3.2 to 4.2 x 10(3) ml(-1) in 8 to 10 g fish and 3.0 to 4.0 x 10(3) ml(-1) in 30 to 40 g fish. M. avidus strain Mie0301 from the Mie prefecture in Japan caused 70% mortality by immersion infection with 4.4 x 10(3) ml(-1) in 30 to 40 g fish. The predominant sign was severe abdominal distension in i.p.-injected fish, and extensive ulcer lesions in the skeletal muscle in immersion-infected fish. Numerous ciliates were observed in the ascetic fluid, ulcers, haemorrhagic lesions, gills and brain of infected fish. However, P. persalinus (strain SCL-A), P. hargisi (strain SCL-B) and U. marinum (strain JK3) showed less than 30% mortality from both i.p. and immersion challenges, with no ciliate invasion in the skin, gills or brain. M. avidus-infected fish showed many ciliates in gills, fins, skin muscle, brain and intestine accompanied by necrosis and haemorrhages. However, no histological changes were observed in P. persalinus-, P. hargisi- or U. marinum-infected fish.
  • Manami Inaba, Satoru Suzuki, Shin-Ichi Kitamura, Norichika Kumazawa, Hiroshi Kodama
    JOURNAL OF MICROBIOLOGY 47 (1) 76 - 84 1225-8873 2009/02 [Peer-reviewed]
     Scientific journal 
    Distribution of marine type of Aquabirnavirus (MABV) was examined in shellfish and fish from Okinawa and Ishigaki Islands, Japan, where water temperature is higher than 25A degrees C through the year. Genome detection and virus isolation were performed for shellfish and fish samples, and the results revealed the prevalent distribution of MABV in diverse species in the area, although isolation was not frequently. Detection rate of MABV genome in bivalves was higher than gastropods, which was similar result to former report in mainland of Japan. Furthermore, the unique five-nucleotide deletion was found with a high rate of occurrence in the MABV genome from shellfish and fish. This study showed distribution status of MABV in organisms in subtropical waters by wide monitoring, and discovered new genome variation in VP2/NS region of this virus.
  • Sogo Nishimoto, Manami Yamawaki, Koichi Akiyama, Yoshimi Kakinuma, Shin-Ichi Kitamura, Takuya Sugahara
    J. Toxicol. Sci. 34 (2) 239 - 244 0388-1350 2009
  • Sung-Ju Jung, Seok-Ryel Kim, Il-Yong Joung, Shin-Ichi Kitamura, Hee-Taek Ceong, Myung-Joo Oh
    JOURNAL OF MICROBIOLOGY 46 (3) 265 - 273 1225-8873 2008/06 Scientific journal 
    Surveys of marine birnavirus (MABV) were undertaken in Cultured olive flounder Paralichthys olivaceus from the south and west coastal areas and Jeju in Korea during the period January 1999 to April 2007. MABV was detected in all seasons from the fry, juveniles and adult fish from the areas examined. Evident cytopathic effects of the virus including rounding and cell lysis were observed in Chinook salmon embryo (CHSE-214) and rainbow trout gonad (RTG-2) cells, but not in fathead minnow (FHM) and epithelial papilloma of carp (EPC) cells. Nucleotide sequences of the VP2/NS junction region of the Korean isolates showed 97.8%similar to 100% similarity, and they belonged to the same genogroup. Cross neutralization tests with serotype-specific rabbit antisera against MABV strains exhibited a close antigenic relationships between strains, and were distinct from infectious pancreatic necrosis virus (IPNV) strains. Coinfection of MABV with bacteria (Streptococcus iniae, Vibrio spp.) and viruses (nervous necrosis virus, lymphocystis disease virus, viral hemorrhagic septicemia virus) was observed.
  • Bo-Kyung Lee, Toshiya Katano, Shin-Ichi Kitamura, Myung-Joo Oh, Myung-Soo Han
    JOURNAL OF MICROBIOLOGY 46 (3) 274 - 282 1225-8873 2008/06 Scientific journal 
    The red tide of dinoflagellate, Cochlodinium polykrikoides has frequently occurred in coastal waters, causing severe damage to fisheries. In the present study, the algicidal bacterium Alteromonas sp. A14 isolated from the southern coast of Korea was applied to a red tide of C. polykrikoides in a laboratory experiment. In the experiment, the abundance of the strain A14 was monitored using fluorescence in situ hybridization. Inoculation of the A14 at a final cell density of 9.0x10(5) cells/ml caused a significant decrease in C. polykrikoides abundance from 1,830 to 700 cells/ml during 2 days, while abundances of harmless diatoms rapidly increased from 3 days. Abundances of both A14 and other bacteria increased to I day. After I day, with flagellate abundance increased, bacterial abundance decreased. Finally, algicidal bacterial abundance decreased to 3.5x10(4) cells/ml. In the biological control of harmful algal blooms, in addition to decrease in target algal abundance and not occurrence of other harmful blooms, decrease in abundance of utilized organism is also important. This study emphasizes the importance of monitoring the inoculated bacterium when applying bacterium to natural seawater.
  • E. Hashimoto, T. Miyadai, M. Ohtani, S-I Kitamura, J. Oh
    JOURNAL OF FISH DISEASES 31 (6) 443 - 449 0140-7775 2008/06 Scientific journal 
    Kuchijirosho is a fatal disease of commercially cultured fugu, Takifugu rubripes. The transmissible nature of kuchijirosho strongly suggests that an infectious pathogen is the causative agent. Because it is filtrable, the agent is thought to be a virus; however, it has not yet been identified. The lack of a permissive cell line for the putative kuchijirosho-causing agent (KCA) has hindered research on the identification of this pathogen. We inoculated brain extract prepared from kuchijirosho-affected fugu onto an established fugu cell line, fugu eye, and observed that cytopathic effect appeared 7 days after inoculation. Injection of the culture medium of infected fugu eye cells into fugu resulted in the onset of kuchijirosho, indicating that fugu eye cells are able to proliferate KCA. An infectious fraction separated by sodium iottalamate density gradient centrifugation showed a density of 1.15 g mL(-1) equivalent to that of KCA derived from affected fugu brain. To determine whether the genome of KCA is RNA or DNA based, nucleotide synthesis inhibitors were applied to inoculated fugu eye cell line to influence the production of KCA. 5-Fluorouracil but not IUdR showed a concentration-dependent inhibition of KCA yield. These results suggest that KCA is an RNA virus.
  • M. Hossain, J-Y Song, S-I Kitamura, S-J Jung, M-J Oh
    JOURNAL OF FISH DISEASES 31 (6) 473 - 479 0140-7775 2008/06 Scientific journal
  • Jun-Young Song, Shin-Ichi Kitamura, Sung-Ju Jung, Toshiaki Miyadai, Shinji Tanaka, Yutaka Fukuda, Seok-Ryel Kim, Myung-Joo Oh
    JOURNAL OF MICROBIOLOGY 46 (1) 29 - 33 1225-8873 2008/02 Scientific journal 
    Viruses belonging to the genus Megalocytivirus in the family Iridoviridae have caused mass mortalities in marine and freshwater fish in Asian countries. In this study, partial major capsid protein (MCP) gene of seven Japanese and six Korean megalocytiviruses was sequenced and compared with the known megalocytiviruses to evaluate genetic variation and geographic distribution of the viruses. Comparison of MCP gene nucleotide sequences revealed sequence identity of 92.8% or greater among these 48 isolates. A phylogenetic tree clearly revealed three clusters: genotype I including nine Japanese isolates, thirteen Korean isolates, one Chinese isolates, one Thailand isolate and one South China Sea isolate; genotype II including five freshwater fish isolates in Southeast Asian countries and Australia; and the remaining genotype III mainly consisted of flatfish isolate in Korea and China. This suggests that viruses belonging to the genotype I widely distribute among various fish species in many Asian countries. Conversely, the epidemic viruses belonged to genotype II and III are may be still locally spreading and constrained in their prevalence to the limited host fish species, i.e., genotype II viruses mainly distribute in Southeast Asian countries, whereas genotype III viruses distribute in flatfish species in Korea and China.
  • Yasunori Murakami, Shin-Ichi Kitamura, Kei Nakayama, Satoru Matsuoka, Hideo Sakaguchi
    MARINE POLLUTION BULLETIN 57 (6-12) 524 - 528 0025-326X 2008 Scientific journal 
    It is well known that heavy oil (HO) on the sea surface causes serious problems in the aquatic environment. In particular, some species of teleosts which develop on the sea surface are thought to be affected by the HO which flows out from tankers or coastal industry. However, the toxicological effects of HO are not fully understood. We performed exposure experiments using the Pleuronectiformean fish, spotted halibut (Verasper variegatus), which is an important fishery resource in Japan. In course of the development, HO-exposed embryos showed remarkable delay in developmental processes including somite formation. We further observed abnormal development of the head morphology. Notably, treated embryos had relatively small eyes and craniofacial structures. These findings strongly suggest that HO seriously affects the cell proliferation and differentiation of the embryo. In addition, HO-exposed embryos showed abnormal neuronal development. We also performed the exposure in the larval stage. Treatment of post-hatching larvae with HO resulted in significantly greater mortality compared with controls. Through these observations, we finally conclude that HO is strongly toxic to halibut in their early life stages. (c) 2008 Elsevier Ltd. All rights reserved.
  • 仲山 慶, 酒井 大樹, 北村 真一, 須藤 明子, 金 恩英, 田辺 信介, 岩田 久人
    環境毒性学会誌 11 (2) 75 - 81 1882-5958 2008
  • Cumulative mortality in striped beackperch, Oplegnathus fasciatus infected with red sea bream iridovirus (RSIV) at different water temperature and identification of heat shock protein 70
    J. Fish Pathol. 21 13 - 20 2008
  • Jun-Young Song, Kei Nakayama, Yasunori Murakami, Sung-Ju Jung, Myung-Joo Oh, Satoru Matsuoka, Hidemasa Kawakami, Shin-Ichi Kitamura
    MARINE POLLUTION BULLETIN 57 (6-12) 889 - 894 0025-326X 2008 Scientific journal 
    As basic research for the effect of heavy oil on the fish immune system, in this study, the number of leukocyte was counted in Japanese flounder Paralichthys olivaceus, after exposure to heavy oil at a concentration of 30 g/8 L for 3 days. To compare the numbers of bacteria in the skin mucus between oil-exposed and control fish, viable bacteria were enumerated by counting colony forming unit (CFU). Compared with 5.79 +/- 1.88 x 10(7) leukocytes/mL in the controls, the exposed fish demonstrated higher counts, averaging 1.45 +/- 0.45 x 10(8) cells/mL. The bacterial numbers of control fish were 4.27 +/- 3.68 x 10(4) C FU/g, whereas they were 4.58 +/- 1.63 x 10(5) CFU/g in the exposed fish. The results suggest that immune suppression of the fish occurred due to heavy oil stressor, and bacteria could invade in the mucus, resulting in the increasing leukocyte number to prevent infectious disease. (C) 2008 Elsevier Ltd. All rights reserved.
  • Kei Nakayama, Shin-Ichi Kitamura, Yasunori Murakami, Jun-Young Song, Sung-Ju Jung, Myung-Joo Oh, Hisato Iwata, Shinsuke Tanabe
    MARINE POLLUTION BULLETIN 57 (6-12) 445 - 452 0025-326X 2008 Scientific journal 
    Heavy oil contamination is one of the most important environmental issues. Toxicities of polycyclic aromatic hydrocarbons (PAHs), including immune toxicities, are well characterized, however, the immune toxic effects of heavy oil, as a complex mixture of PAHs, have not been investigated. In the present study, we selected Japanese flounder (Paralichthys olivaceus) as a model organism, and observed alteration of immune function by the exposure to heavy oil. To analyze the expression profiles of immune system-related genes, we selected 309 cDNAs from our flounder EST library, and spotted them on a glass slide. Using this cDNA array, alteration of gene expression profiles was analyzed in the kidneys of flounders exposed to heavy oil. Six Japanese flounders (mean body weight: 197 g) were acclimated to laboratory conditions at 19-20 degrees C. Three fish were exposed to heavy oil C (bunker C) at a concentration of 3.8 g/L for 3 days, and the others were kept in seawater without heavy oil and used as the control. After the exposure period, the fish were transferred into control seawater and maintained for 4 days, and then they were dissected and their kidneys were removed. Total RNA was extracted from the kidney samples to use in gene expression analyses. The microarray detected alteration of immune system-related genes in the kidneys of heavy oil-exposed flounders, including down-regulation of immunoglobulin light chain, CD45, major histocompatibility complex class II antigens and macrophage colony-stimulating factor precursor, and up-regulation of interleukin-8 and lysozyme. These results suggest that pathogen resistance may be weakened in heavy oil-exposed fish, causing a subsequent bacterial infection, and then proinflammatory genes may be induced as a defensive response against the infection. Additionally, we found candidate genes for use as biomarkers of heavy oil exposure, such as N-myc downstream regulated gene 1 and heat shock cognate 71 kDa proteins. (c) 2008 Elsevier Ltd. All rights reserved.
  • Kaoru Azumi, Takeshi Usami, Akiko Kamimura, Sorin V. Sabau, Yasufumi Miki, Manabu Fujie, Sung-Ju Jung, Shin-Ichi Kitamura, Satoru Suzuki, Hideyoshi Yokosawa
    ZOOLOGICAL SCIENCE 24 (12) 1231 - 1240 0289-0003 2007/12 Scientific journal 
    A serious disease of the ascidian Halocynthia roretzi has been spread extensively among Korean aquaculture sites. To reveal the cause of the disease and establish a monitoring system for it, we constructed a cDNA microarray spotted with 2,688 cDNAs derived from H. roretzi hemocyte cDNA libraries to detect genes differentially expressed in hemocytes between diseased and non-diseased ascidians. We detected 21 genes showing increased expression and 16 genes showing decreased expression in hemocytes from diseased ascidians compared with those from non-diseased ascidians. RT-PCR analyses confirmed that the expression levels of genes encoding astacin, lysozyme, ribosomal protein PO, and ubiquitin-ribosomal protein L40e fusion protein were increased in hemocytes from diseased ascidians, while those of genes encoding HSP40, HSP70, fibronectin, carboxypeptidase and lactate dehydrogenase were decreased. These genes were expressed not only in hemocytes but also in various other tissues in ascidians. Furthermore, the expression of glutathione-S transferase omega, which is known to be up-regulated in H. roretzi hemocytes during inflammatory responses, was strongly increased in hemocytes from diseased ascidians. These gene expression profiles suggest that immune and inflammatory reactions occur in the hemocytes of diseased ascidians. These genes will be good markers for detecting and monitoring this disease of ascidians in Korean aquaculture sites.
  • Shin-Ichi Kitamura, Jin-Yong Ko, Wol-La Lee, Seok-Ryel Kim, Jun-Young Song, Dong-Kyu Kim, Sung-Ju Jung, Myung-Joo Oh
    AQUACULTURE 266 (1-4) 26 - 31 0044-8486 2007/06 Scientific journal 
    Japanese flounder, Paralichthys olivaceus, is the most important commercial fish in Korea, and viral diseases in this fish cause important economic losses. To control fish viral diseases, an understanding of the viral dynamics in the host fish and also in viral vectors and/or reservoirs is needed. In this study, polymerase chain reaction (PCR) was used to investigate seasonal changes of lymphocystis disease virus (LCDV), aquatic birnavirus (ABV), viral haemorrhagic septicaemia virus (VHSV) and megalocytivirus in Japanese flounder. Level of antibody titers in flounder sera against ABV was also determined by a neutralization test. In addition, because wild blue mussel Mytilus galloprovincialis is considered a candidate for the vector and/or reservoir of the viruses, PCR was performed to determine if viruses were present in the shellfish collected near the aquaculture facilities. During the course of fish development from juvenile size to commercial size, ten fish and ten shellfish were collected monthly from a Korean aquaculture farm. They were used for virus detection by PCR. Sera from the fish collected at the end of the study were examined for antibody titers. Neither megalocytivirus nor VHSV was detected by PCR in any of the fish or shellfish collected throughout the experimental period. LCDV was detected in the fish collected in August and November, and the detection rates of the virus were 50% and 10%, respectively. Regarding the two peaks of virus detection, LCDV most probably extensively replicates in Japanese flounder in summer, when the water temperature is around 20 degrees C because the virus can grow from 20 to 25 degrees C in cell lines such as HINAE and GCO. In winter, the virus would have been able to replicate in the fish that had not previously acquired antibodies against the virus. ABV was detected in 10% of the fish collected in July and August. Although the ABV detection rate was low in the fish during the observation period, almost all the fish collected in November had neutralization antibody titers (> 1:128). The fish may acquire neutralization antibodies against the virus during seeding production, because the disease primarily occurs in hatcheries in Korea, and/or in aquatic environments, such as seawater, where the virus is quite common. ABV was also detected in blue mussels around the same time that the virus was detected in the fish, suggesting that the shellfish may be a vector and/or reservoir for the virus. (c) 2007 Elsevier B.V. All rights reserved.
  • Kaoru Azumi, Shinli Nakamura, Shin-Ichi Kitamura, Sung-Ju Jung, Keisuke Kanehira, Hisato Iwata, Shinsuke Tanabez, Satoru Suzuki
    FISHERIES SCIENCE 73 (2) 263 - 269 0919-9268 2007/04 Scientific journal 
    Recently, a serious disease spread extensively in aquaculture sites of the ascidian Halocynthia roretzi in Korea. To understand circumstances of ascidians in Korean aquaculture sites, residue levels of organotin compounds were analyzed, and detection of a marine birnavirus (MABV) in tissues of H. roretzi was attempted. Korean H. roretzi showed high concentrations of butyltins (mono, di, and tributyltins), especially in the gill, hepatopancreas, and digestive tract. However, there was no significant difference in the residues of butyltins in the hepatopancreas between diseased and non-diseased ascidians. The positive rate of MABV detection was high in the hepatopancreas, but also no significant difference was observed between diseased and non-diseased individuals. These observations suggest that an accumulation of tributyltin and a latency of MABV in H. roretzi tissues does not directly relate to the occurrence of the disease.
  • Miamiensis avidus (Ciliophora: Scuticociliatida) causing systemic infection against olive flounder Paralichthys olivaceus and confirmation of M. avidus as a senior synonym of Philasterides dicentrarchi.
    Dis. Aquat. Org. 73 227 - 234 2007
  • Sung-Ju Jung, Shin-Ichi Kitamura, Jun-Young Song, Myung-Joo Oh
    DISEASES OF AQUATIC ORGANISMS 73 (3) 227 - 234 0177-5103 2007/01 [Peer-reviewed]
     Scientific journal 
    The scuticociliate Miamiensis avidus was isolated from olive flounder Paralichthys olivaceus showing typical symptoms of ulceration and hemorrhages in skeletal muscle and fins. In an infection experiment, olive flounder (mean length: 14.9 cm; mean weight: 26.8 g) were immersion challenged with 2.0 x 10(3), 2.0 x 10(4) and 2.0 x 10(5) ciliates ml(-1) of the cloned YS1 strain of M avidus. Cumulative mortalities were 85% in the 2.0 x 10(3) cells ml(-1) treatment group and 100% in the other 2 infection groups, Many ciliates, containing red blood cells in the cytoplasm, were observed in the gills, skeletal muscle, skin, fins and brains of infected fish, which showed accompanying hemorrhagic and necrotic lesions, Ciliates were also observed in the lamina propria of the digestive tract, pharynx and cornea. The fixed ciliates were 31.5 +/- 3.87 mu m in length and 18.5 +/- 3.04 mu m in width, and were ovoid and slightly elongated in shape, with a pointed anterior and a rounded posterior, presenting a caudal cilium. Other morphological characteristics were as follows: 13 to 14 somatic kineties, oral ciliature comprising membranelles M1, M2, M3, and paroral membranes PM1 and PM2, contractile vacuole at the posterior end of kinety 2, shortened last somatic kinety and a buccal field to body length ratio of 0.47 +/- 0.03. In addition, continuous PM1 and PM2, lack of M3 and variable kinetosome numbers in M2 and M3 were frequently observed. Specimens in the current study were compared with previous reports on M avidus and Philasterides dicentrarchi and confirmed consistently that these 2 taxa are conspecific.
  • MJ Oh, WS Kim, SI Kitamura, HK Lee, BW Son, TS Jung, SJ Jung
    AQUACULTURE 257 (1-4) 156 - 160 0044-8486 2006/06 Scientific journal 
    Recently, mass mortality of adult nounder showing ascites occurred at many aquaculture farms in Korea. While we investigated the cause of the mortality, marine birnavirus (MABV-F) and bacteria (Vibrio harveyi and Edwardsiella tarda) were isolated from diseased fish. By the intraperitoneal (IP) injection with MABV-F, the virus strain did not show pathogenicity to the flounder. When the fish co-infected with MABV-F (IP) and V harveyi or E. tarda (immersion), the cumulative mortality did not show any significant difference with control group. In contrast, the case of co-infection with MABV-F and bacteria by IP, cumulative mortality reached more than 90%. Most of the moribund and dead fish except for the mock-infected fish displayed ascites, and the virus and bacteria were re-isolated from all the dead and moribund fish except for the control fish. The results indicate that the cause of mass mortality of the adult fish may be due to bacterial infection. Higher mortalities may occur due to co-infection of MABV-F and bacteria, although MABV-F alone did not cause direct mortality. (c) 2006 Elsevier B.V. All rights reserved.
  • SI Kitamura, SJ Jung, MJ Oh
    JOURNAL OF MICROBIOLOGY 44 (2) 248 - 253 1225-8873 2006/04 Scientific journal 
    Lymphocystis disease virus (LCDV) is the causative agent of lymphocystis disease. The viruses have been divided into three genotypes (genotype I for LCDV-1, II for Japanese flounder isolates, and III for rockfish isolates) on the basis of major capsid protein (MCP) gene sequences. In this study, we developed a multiplex PCR primer set in order to distinguish these genotypes. We also analyzed the MCP gene of a new LCDV isolate from the sea bass (SB98Yosu). Comparison of sequence identities between SB98Yosu and eight Japanese flounder isolates, revealed identity of more than 90.1% at nucleotide level and 96.5% at deduced amino acid level, respectively. Phylogenetic analyses based on the MCP gene showed that SB98Yosu belongs to genotype II, along with Japanese flounder isolates. Multiplex PCR based on the MCP gene allowed us to identify these genotypes in a simple and rapid manner, even in a sample that contained two genotypes, in this case genotypes II and III.
  • SI Kitamura, SJ Jung, WS Kim, T Nishizawa, M Yoshimizu, MJ Oh
    ARCHIVES OF VIROLOGY 151 (3) 607 - 615 0304-8608 2006/03 Scientific journal 
    Lymphocystis disease virus (LCDV) is the causative agent of lymphocystis disease. In this study, nucleotide sequences of the major capsid protein (MCP) gene were analyzed among LCDV isolates from Japanese flounder and rockfish. A phylogenetic tree revealed three clusters for lymphocystiviruses. The first cluster included Japanese flounder isolates; the second cluster consisted of rockfish isolates; and the remaining one consisted of LCDV-1. Nucleotide sequence identities were >= 99.6% among Japanese flounder isolates and 100% among rockfish isolates, while between each cluster they were <= 85.2%. Experimental infections with Japanese flounder and rockfish isolates revealed that Japanese flounder and rockfish were infected by the respective homologous isolate but not by the heterologous isolate. These findings suggest that at least three genotypes exist in the genus Lymphocystivirus.
  • Acute toxicity of wood vinegar on culture fishes
    J. Fish Pathol. 19 277 - 284 2006
  • Viral diseases of olive flounder in Korean hatchery
    J. Ocean Univ. China 5 44 - 48 2006
  • Nervous necrosis virus (NNV)-free seed production of red drum, Sciaenops ocellatus
    J. Fish Pathol. 19 65 - 72 2006
  • Immune response of olive flounder, Paralichthys olivaceus against Miamiensis avidus (Ciliophora: Scuticociliatida)
    J. Fish Pathol. 19 173 - 181 2006
    J. Fish Dis. 29 (7) 415 - 421 0140-7775 2006
  • WS Kim, MJ Oh, SJ Jung, YJ Kim, SI Kitamura
    DISEASES OF AQUATIC ORGANISMS 64 (2) 175 - 180 0177-5103 2005/04 Scientific journal 
    Juvenile turbot Scophthalmus maximus that became sick during an outbreak of disease at mariculture facilities at Go-Chang, Korea, in 2003, were examined to identify the cause of the disease. The fish had pale body color, an enlarged abdomen, protruding eyes, an enlarged spleen and kidney, and pale gills and/or liver. Histopathogical examination revealed basophilic enlarged cells in the kidney, spleen, gills, heart, stomach, intestine, liver, pancreas and skin. Hexagonal viral particles with a diameter of 136 to 159 nm were observed in the enlarged cells. A specific 1299 bp fragment of the major capsid protein (MCP) gene of the turbot iridovirus (TBIV) was amplified by PCR. Sequence homology was greater than 93.76% between the MCP gene in TBIV and the same gene in 5 viruses in the tentatively proposed genus Tropivirus (family Iridoviridae): red sea bream iridovirus, sea bass iridovirus, grouper sleepy disease iridovirus, African lampeye iridovirus and dwarf gourami iridovirus. These results suggest that the virus detected from turbot is similar to the proposed genus Tropivirus.
  • SJ Jung, SI Kitamura, JY Song, IY Joung, MJ Oh
    DISEASES OF AQUATIC ORGANISMS 64 (2) 159 - 162 0177-5103 2005/04 Scientific journal 
    Eight isolates of Miamiensis avidus (scuticociliates) were collected from olive flounder Paralichthys olivaceus with symptoms of severe ulcers and haemorrhages at several culture farms in 1999 and 2003. Cloned strains were produced and the complete small subunit ribosomal RNA gene (SSU rRNA) of each strain was sequenced for classification and phylogenic study. The SSU rRNA is 1759 bp in length and the sequence was deposited in the GenBank under accession number AY550080. All 8 strains exhibited the same sequence, but this sequence did not match any previously deposited scuticociliate SSU rRNA sequence. Phylogenetic analysis placed Miamiensis avidus in a sister lineage to Cohnilembus verminus, Pseudocohnilembus hargisi and P. marinus.
  • A comparative study based on RT-PCR and sequence analysis of nervous necrosis virus (NNV) infecting marine fishes in Korea
    J. World Aquacult. Soc. 36 223 - 227 2005
  • SI Kitamura, SI Kamata, SI Nakano, S Suzuki
    DISEASES OF AQUATIC ORGANISMS 58 (2-3) 251 - 254 0177-5103 2004/03 Scientific journal 
    We examined the inactivation kinetics of marine birnavirus (MABV) in a coastal sea, in seawater samples collected from 50 cm depth. MABV was added to both natural and autoclaved seawater at a concentration of 6 x 10(6.43) TCID50 (50% tissue culture infectious close) ml(-1), put in dialysis tubes and incubated at the original depth. The inactivation of MABV by solar UV radiation was examined using light and dark tubes. The infectivity titer of MABV was measured by the TCID50 method using CHSE-214 cells. Virus infectivity in natural seawater decreased quickly and was below the detection limit by 270 min in both light and dark conditions; however, virus infectivity was maintained in the autoclaved seawater until 420 min. These results suggest that the loss of virus infectivity is not caused by sunlight UV radiation.
  • Molecular characterization of infected iridovirus in cultured turbot (Scophthalmus maximus)
    J. Aquaculture 17 24 - 29 2004
  • S Nakano, Y Tomaru, T Katano, A Kaneda, W Makino, Y Nishibe, M Hirose, M Onji, S Kitamura, H Takeoka
    AQUATIC ECOLOGY 38 (4) 485 - 493 1386-2588 2004 Scientific journal 
    Seasonal changes in abundance of planktonic microorganisms, together with some physico-chemical variables, were monitored monthly from May 1999 to March 2002 in the surface water of a coastal bay where nutrients are mainly supplied by intermittent intrusions of deeper water (bottom intrusion). No significant bottom intrusion was detected in 1999 but large or frequent bottom intrusions were found from June to October in 2000, and again from mid-June only to late July in 2001. These results indicate that there is a different nutrient supply every year, and peaks in the abundance of dominant eukaryotic phytoplankton (diatoms and dinoflagellates) roughly corresponded to the occurrences of bottom intrusions. By contrast, there was a cyclic seasonal pattern of autotrophic picoplankton (APP) cell density, which reached maxima in August of every year at very similar levels (4.0-5.0 X 10(5) cells ml(-1)). Thus, the seasonal abundance of APP was apparently independent of the occurrence of bottom intrusions. Seasonal changes in cell densities of heterotrophic bacteria showed similar trends to the APP, and temperature-dependent growth of both was indicated. The present study suggests that the matter cycling in the bay varies as a result of shifts in the dominant food linkages, from a microbial food web to a herbivorous food web, due to intermittent nutrient supplies from bottom intrusions.
  • S Kitamura, S Kamata, S Nakano, S Suzuki
    DISEASES OF AQUATIC ORGANISMS 54 (1) 69 - 72 0177-5103 2003/03 Scientific journal 
    Marine birnaviruses (MABVs) infect a wide range of fish and shellfish, yet their mode of transmission is still unclear. To determine whether marine plankton serve as a vector for MABVs, we examined plankton collected from the Uwa Sea, Japan. The phytoplankton and zooplankton were collected monthly, at depths of 0 and 40 m, from May to November 2001. Detection of the MABV genome was carried out using 2-step PCR and virus isolation. Viral genome was detected in zooplankton collected at 0 m depth in September and at 40 m depth in November. The virus could not be isolated in the PCR-positive samples. These results suggest that zooplankton may act as a vector of MABVs, although the infective and/or accumulated virus titer in zooplankton was low.
  • G protein gene of infectious hematopoietic necrosis Virus (IHNV) isolated from adult rainbow trout, Salmo gairneri in Korea
    J. Fish Pathol. 16 161 - 164 2003
  • The infection of irido-like virus in cultured turbot (Scophthalmus maximus)
    J. Fish Pathol. 16 153 - 159 2003
  • SI Kitamura, Y Tomaru, Z Kawabata, S Suzuki
    DISEASES OF AQUATIC ORGANISMS 50 (3) 211 - 217 0177-5103 2002/07 Scientific journal 
    This study examines the seasonal changes of marine birnavirus (MABV) in seawater and the Japanese pearl oyster Pinctada fucata reared at different depths (2 and 15 in). Oysters and seawater were collected in 1998, and a 2-step PCR was carried out to detect MABV. Virus isolation was performed on the PCR-positive samples in the oyster. The detection rate of the MABV genome in the oyster was low during June, but increased after July at both 2 and 15 in depths. MABV was not isolated until after September, when isolation rates of 10 to 28.6 % were recorded. The results suggest that growth of MABV in the oyster is similar at 2 and 15 in depth. In contrast, the MABV genome in seawater was present through the year at 15 in depth, but was not detected in summer at 2 in. This suggests that the virus is destroyed by UV and/or other factors at 2 in in summer, but is stable in deeper waters.
  • T Miyadai, SI Kitamura, H Uwaoku, D Tahara
    DISEASES OF AQUATIC ORGANISMS 47 (3) 193 - 199 0177-5103 2001/12 Scientific journal 
    Kuchijirosho (snout ulcer disease) is a fatal epidemic disease which affects the tiger puffer, Takifugu rubripes, a commercial fish species in Japan and Korea. To assess the possibility that non-tiger puffer fish can serve as reservoirs of infection, 5 fish species were challenged by infection with the extracts of Kuchijirosho-affected brains from cultured tiger puffer: grass puffer T. niphobles, fine-patterned puffer T. poecilonotus, panther puffer T. pardalis, red sea bream Pagrus major, and black rockfish Sebastes schlegeli, When slightly irritated, all these species, especially the puffer fish, exhibited typical signs of Kuchijirosho, i.e., erratic swimming, biting together and bellying out (swelling of belly), as generally observed in tiger puffers affected by Kuchijirosho, Although the mortalities of the 2 non-puffer species were lower, injection of the extracts prepared from the brains of both inoculated fish into tiger puffer resulted in death, indicating that the inoculated fish used in this experiment have the potential to be infected with the Kuchijirosho agent. Condensations of nuclei or chromatin in the large nerve cells, which is a major characteristic of Kuchijirosho, were histopathologically observed to some extent in the brains of all kinds of puffer fish species infected, These findings suggest that the virus can spread horizontally among wild and cultured puffers and even among fishes belonging to different orders.
  • Satoru Suzuki, Shin-Ichi Kitamura, Hiroshi X. Chiura
    Microbes and Environments 16 (3) 191 - 196 1347-4405 2001 Scientific journal 
    Marine birnavirus (MABV) is a member of Aquabirnavirus and an opportunistic pathogenic virus in eukaryotic marine organisms. This virus has a broad host range in wild and cultured fish and shellfish. In this study, the distribution of MABV in seawater from different areas was examined by PCR of the VP2/Ns junction region of the MABV genome. We have detected the MABV genome in three marine water columns off the coast of Japan, in the Pacific Ocean and in the Mediterranean Sea, suggesting that MABV is widely distributed. The MABV genome was also detected in samples of zooplankton from the Pacific Ocean. A high nucleotide sequence similarity (more than 98.5%) was observed among the PCR products from MABV genomes. Such a prevalent distribution of genetically similar MABV suggests that birnavirus is one of the components of the RNA pool in ocean environments. © 2001, Japanese Society of Microbial Ecology & The Japanese Society of Soil Microbiology. All rights reserved.
  • SI Kitamura, S Suzuki
    MARINE BIOTECHNOLOGY 2 (2) 188 - 194 1436-2228 2000/03 Scientific journal 
    This study aims to determine the seasonal occurrence of marine birnavirus (MABV) at a coastal site in the Uwa Sea, Japan, in 1997 and 1998. To detect MABV from seawater, a simple method was developed for concentrating MABV by dialysis and ethanol precipitation. The concentrated virus was used for polymerase chain reaction (PCR), enzyme-linked immunosorbent assay, and virus isolation. Viral genome was detected through the experimental period. The amount of PCR product varied; it was small in summer, but increased from fall to winter. Viral protein was also detected, and the amount in the January sample was equivalent to approximately 10(2) TCID50 (50% tissue culture infectious dose) of the virus. However, infectious viruses were not isolated. This suggested that MABV was released from hosts to environmental seawater in winter and possibly degraded after release.
    Arch. Virol. 145 (10) 2003 - 2014 1432-8798 2000
  • SJ Jung, SI Kitamura, K Kawai, S Suzuki
    DISEASES OF AQUATIC ORGANISMS 38 (2) 87 - 91 0177-5103 1999/11 Scientific journal 
    A birnavirus was recently isolated from cultured ayu Plecoglossus altivelis on Shikoku island, Japan. The diseased fish displayed vertebral or vertical curvature and mild haemorrhage around the brain. Cytopathic effects (CPE) of the virus, including cell roundness, filamentous change and cell lysis, were observed in CHSE-214, RTG-2 and RSBK-2 cells. The virus isolated from ayu, designated the AY-98 strain, was found to be antigenically related to the marine birnavirus (MABV) Y-6 strain that originated from yellowtail Seriola quinqueradiata. AY-98 had a bi-segmented RNA genome and the same nucleotide sequence in the 310 bp VP2/NS junction as MABV Y-6. At the same time that the ayu epizootics occurred, another birnavirus (AM-98) was isolated from amago salmon Oncorhynchus rhodurus which were cultured 66 km away from the ayu farm. AM-98 showed a similar CPE and had the same host cell ranges as AY-98. However, AM-98 was serologically similar to the VR-299 strain of infectious pancreatic necrosis virus (IPNV) and their nucleotide sequences in the VP2/ NS junction region showed 98% homology without changes at the amino acid level. In this study, the ayu strain AY-98 was grouped into MABV, whereas the amago salmon strain AM-98 was grouped into IPNV. This indicates that the 2 birnaviruses originated from different sources in spite of the fact that the places where they were isolated are close to one another. The results in this paper show a new aspect of the traditional consensus that the same serogroup of birnavirus distribute in close geographic areas.
  • SJ Jung, SI Kitamura, K Kawai, S Suzuki
    DISEASES OF AQUATIC ORGANISMS 38 (2) 87 - 91 0177-5103 1999/11 [Peer-reviewed]
     Scientific journal 
    A birnavirus was recently isolated from cultured ayu Plecoglossus altivelis on Shikoku island, Japan. The diseased fish displayed vertebral or vertical curvature and mild haemorrhage around the brain. Cytopathic effects (CPE) of the virus, including cell roundness, filamentous change and cell lysis, were observed in CHSE-214, RTG-2 and RSBK-2 cells. The virus isolated from ayu, designated the AY-98 strain, was found to be antigenically related to the marine birnavirus (MABV) Y-6 strain that originated from yellowtail Seriola quinqueradiata. AY-98 had a bi-segmented RNA genome and the same nucleotide sequence in the 310 bp VP2/NS junction as MABV Y-6. At the same time that the ayu epizootics occurred, another birnavirus (AM-98) was isolated from amago salmon Oncorhynchus rhodurus which were cultured 66 km away from the ayu farm. AM-98 showed a similar CPE and had the same host cell ranges as AY-98. However, AM-98 was serologically similar to the VR-299 strain of infectious pancreatic necrosis virus (IPNV) and their nucleotide sequences in the VP2/ NS junction region showed 98% homology without changes at the amino acid level. In this study, the ayu strain AY-98 was grouped into MABV, whereas the amago salmon strain AM-98 was grouped into IPNV. This indicates that the 2 birnaviruses originated from different sources in spite of the fact that the places where they were isolated are close to one another. The results in this paper show a new aspect of the traditional consensus that the same serogroup of birnavirus distribute in close geographic areas.

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  • マボヤ被嚢軟化症の防疫対策に関する研究
    Date (from‐to) : 2015/04 -2018/03 
    Author : 北村 真一
  • マボヤ被嚢軟化症の被嚢軟化メカニズムの解明
    Date (from‐to) : 2013/04 -2016/03 
    Author : 北村 真一
  • リンホシスチスウイルス感染による宿主細胞の肥大化機構の解明
    文部科学省:科学研究費補助金 若手B
    Date (from‐to) : 2011/04 -2013/03 
    Author : 北村 真一
  • アジュバントを用いた世界初の魚類寄生虫ワクチンの開発
    Date (from‐to) : 2009/04 -2010/03 
    Author : 北村 真一
  • 重油の魚類感染症および神経異常に発生に与える影響
    文部科学省:科学研究費補助金 若手B
    Date (from‐to) : 2008/04 -2010/03 
    Author : 北村 真一
  • 海洋ウイルスを用いた養殖環境水の新規評価方法の開発
    Date (from‐to) : 2008/04 -2009/03 
    Author : 北村 真一
  • 世界初の魚類寄生虫ワクチンの開発
    Date (from‐to) : 2008/04 -2009/03 
    Author : 北村 真一
  • ヒラメスクーチカ症原因虫の抗原解析〜世界初の魚類寄生虫ワクチンの開発に向けて〜
    Date (from‐to) : 2007/04 -2008/03 
    Author : 北村 真一
  • 沿岸のプランクトンは魚介類病原マリンビルナウイルスのキャリアーか?
    Date (from‐to) : 2002/04 -2003/03 
    Author : 北村 真一




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  • 2019, the first semester, under graduate, 卒業研究Ⅰ
  • 2019, the first semester, under graduate, 海洋生物学
  • 2019, the first semester, under graduate, 海洋生物学

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