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NO35 - 2

Inhibitory Effect of Cortisol on the Degranulation of Eosinophilic Granular Cells in Tilapia

December 6, 1999<>Tomomasa Matsuyama1, Junko Kurogi1 and Takaji Iida2*<>1 United Graduate School of Agricultural Sciences, Kagoshima University, Kourimoto 1-21-24,Kagoshima 890-0065, Japan
2 Faculty of Agriculture, Miyazaki University, Gakuen Kibanadai-Nishi 1-1,Miyazaki 889-2192, Japan

ABSTRACT ・We examined the effect of cortisol on the degranulation and number of eosinophilic granular cells (EGCs) in tilapia, Oreochromis niloticus. One hour after injection of stimulants (killed Escherichia coli or substance P, a neurotransmitter) into the swim bladder, the percent of the degranulated EGCs in the swim bladder membrane was determined. Peritoneal implantation of coconut oil containing cortisol (50 mg/kg body weight) 24 h before injection of stimulants significantly reduced the percent of the degranulated EGCs, compared with the control fish administered with coconut oil without cortisol. Cortisol also suppressed the in vitro degranulation of EGCs stimulated with substance P or with tilapia normal sera containing zymosan. To investigate the effect of cortisol on the abundance of EGCs, the number of EGCs in the swim bladder membrane was counted. Density of EGCs was decreased after implantation of cortisol, compared with that of the control group. These results suggest that cortisol suppresses the degranulating activity of EGCs and decreases the density of EGCs in the tissue.

Tetrahymena Infection in Guppy, Poecilia reticulata

January 19, 2000<>Soichi Imai1*, Sayaka Tsurimaki1, Eiko Goto1, Kunika Wakita2 and Kishio Hatai3 <>1 Division of Veterinary Parasitology, Nippon Veterinary and Animal Science University,1-7-1, Kyonan-cho, Musashino, Tokyo 180-8602, Japan
2 Department of Pathology, Faculty of Veterinary Science, Azabu University, 1-17-71,Fuchinobe, Sagamihara, Kanagawa 229-8501, Japan
3 Division of Fish Diseases, Nippon Veterinary and Animal Science University, 1-7-1,Kyonan-cho, Musashino, Tokyo 180-8602, Japan

ABSTRACT ・Out of 78 diseased guppies imported from Singapore to Japan, 43 fish were found infected with ciliates. Thus, pathological examination of guppies naturally infected with ciliates and identification of a ciliate sampled from guppies in Singapore were conducted. Most of the ciliates parasitized the inside of scales, muscles or internal organs, while some invaded into the eye socket and spinal cord. No damage was found in the intestinal epithelium. From these findings, it is considered that the main invasion route of these ciliates was from the scales of hosts to internal organs through muscles. As the results of morphological examination using silver impregnation, the examined ciliate was identified as Tetrahymena corlissi Thompson, 1955, which has been
reported as a pathogen of guppies in North America.

Bacterial Agglutinins in the Skin Mucus of Japanese Eel

January 19, 2000<>Yuko Kosuga1, Nobuhiro Mano2 and Hitomi Hirose1*<>1 Department of Marine Science and Resources, College of Bioresource Sciences,Nihon University, 1866, Kameino, Fujisawa, Kanagawa 252-8510, Japan
2 National Research Institute of Fisheries Science, 2-12-4, Fukuura, Kanazawa,Yokohama, Kanagawa 236-8648, Japan

ABSTRACT 輸gglutinating activities of the skin mucus extract (SME) from Japanese eel were examined against bacteria isolated from water and skin of reared eels in an experimental aquarium. The SME agglutinated 60 out of 152 bacterial isolates from the rearing water (water group), and 40 out of 130 bacterial isolates from eel skin (skin group). The agglutinating activities tended to be higher against bacterial isolates in the water group than those in the skin group, suggesting the skin mucus agglutinins are efficient for excluding bacteria from the skin. Lactose, which is known as a specific carbohydrate recognized by the eel skin mucus lectin, inhibited agglutination against 36% bacterial isolates in the water group and 35% in the skin group. This result shows that SME contains more than one kind of bacterial agglutinins.

In situ Hybridization for Detection of the Microsporidian Parasite Glugea plecoglossi by Using Rainbow Trout as an Experimental Infection Model

March 6, 2000<>Sun-Joung Lee*, Hiroshi Yokoyama, Kazuo Ogawa and Hisatsugu Wakabayashi<>Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo, Tokyo 113-8657, Japan

ABSTRACT ・Early stages of Glugea plecoglossi (Microspora) are difficult to detect by normal light microscopy. In situ hybridization (ISH) protocol with DIG-labeled oligonucleotide probes designed from SSUrRNA of G. plecoglossi was established with the aim of detecting all stages. All developmental stages of G. plecoglossi in xenomas could be detected by ISH. First, we aimed to evaluate the suitability of rainbow trout as an experimental animal in place of ayu for G. plecoglossi.
Immersion challenge tests showed that the susceptibility and location of G. plecoglossi did not differ between ayu and rainbow trout. Cyst forming sites were different among challenged trout by the three methods (intubation, immersion and intraperitoneal injection). In the intestinal epithelium of rainbow trout (Oncorhynchus mykiss) at 5 min post-intubation of G. plecoglossi spores, we found possible initial stages, which were positive in ISH and negative in Uvitex 2B staining. This finding suggests that G. plecoglossi spores discharging the polar tube pierced the gut epithelial cells, and injected the infective sporoplasm. The present study showed that ISH is a promising tool for studying transmission modes of G. plecoglossi in fish and that rainbow trout is a useful replacement host to identify the pathobiological characteristics of G. plecoglossi.

Effects of Temperature, Salinity and Chlorine Treatment on Egg Hatching of the Monogenean Neoheterobothrium hirame Infecting Japanese Flounder

April 6, 2000<>Tomoyoshi Yoshinaga1*, Isao Segawa1, Takashi Kamaishi1 and Minoru Sorimachi2<>1 Inland Station, National Research Institute of Aquaculture, Tamaki, Mie 519-0423, Japan
2 National Research Institute of Aquaculture, Nansei, Mie 519-0193, Japan

ABSTRACT ・Effects of temperature, salinity and chlorine treatment on egg hatching of the monogenean parasite, Neoheterobothrium hirame, of the Japanese flounder, Paralichthys olivaceus, were examined. More than 85% of the eggs developed and hatched between 10 and 25コC, but at 30コC hatching rates were lower than 5%. They hatched similarly in a wide range of salinities from 1/3- to full-strength seawater (salinity: 11・3・. In distilled water and double-strength seawater, they did not hatch at all. In 1.5-strength seawater, a decrease of hatching rates was observed. Eggs treated with sodium hypochlorite (available chlorine concentrations below 50 ppm for 15 min) showed hatching rates similar to those in the control. Even an extraordinary chlorine treatment (available chlorine concentration 100 ppm for 15 min) had a limited effect on the hatching rates.

Improved Immunity of Tilapia Oreochromis niloticus by C-UP III, a Herb Medicine

October 13, 1999<>Nantarika Chansue1, Aranya Ponpornpisit2, Makoto Endo3*, Masahiro Sakai3 and Satoshi Yoshida4<>1 Veterinary Medical Aquatic Animal Research Center, Faculty of Veterinary Science, Chulalongkorn University, Henri Dunant Rd., Bangkok 10330, Thailand
2 United Graduate School of Agricultural Sciences, Kagoshima University, Kourimoto 1-21-24, Kagoshima 890-0065, Japan
3 Division of Fish Pathology, Faculty of Agriculture, Miyazaki University, Gakuen-Kibanadai Nishi 1-1, Miyazaki 889-2192, Japan
4 Institute for Consumer Healthcare, Yamanouchi Pharmaceutical Co., Ltd., Hasune 3, Itabashi, Tokyo 174-8612, Japan

A Brown Pigment-producing Strain of Pseudomonas plecoglossicida Isolated from Ayu with Hemorrhagic Ascites

November 24, 1999<>Se Chang Park1, Ichiro Shimamura2, Masaru Hagihira2 and Toshihiro Nakai1*<>1 Fish Pathology Laboratory, Faculty of Applied Biological Science, Hiroshima University, Higashihiroshima, Hiroshima 739-8528, Japan
2 Tokushima Prefectural Fisheries Experiment Station, Hiwasa, Tokushima 779-2304, Japan

Sequencing of gyrB and Their Application in the Identification of Flavobacterium psychrophilum by PCR

February 14, 2000<>Shotaro Izumi* and Hisatsugu Wakabayashi<>Graduate School of Agricultural and Life Sciences,The University of Tokyo, Yayoi 1-1-1, Bunkyo,Tokyo 113-8657, Japan

Viral Nervous Necrosis in Humpback Grouper Cromileptes altivelis Larvae and Juveniles in Indonesia

February 14, 2000<>Zafran1, Isti Koesharyani1, Fris Johnny1, Kei Yuasa2, Takahiko Harada3 and Kishio Hatai4*<>1 Gondol Research Station for Coastal Fisheries, P. O. Box 140, Singaraja 81101, Indonesia
2 Japan International Cooperation Agency, Shinjuku Maynds Tower Bldg. 11 th floor, 2-1-1 Yoyogi, Shibuya,Tokyo 151-8558, Japan
3 Division of Biology, Faculty of Veterinary, Nippon Veterinary and Animal Science University, Kyonan-cho 1-7-1, Musashino, Tokyo 180-8602, Japan
4 Division of Fish Diseases, Faculty of Veterinary, Nippon Veterinary and Animal Science University, Kyonan-cho 1-7-1, Musashino, Tokyo 180-8602, Japan

Effects of NaCl-supplemented Seawater on the Monogenean, Neoheterobothrium hirame, Infecting the Japanese Flounder

April 6, 2000<>Tomoyoshi Yoshinaga1*, Takashi Kamaishi1, Isao Segawa1 and Eiichi Yamamoto2<>1 Inland Station, National Research Institute of Aquaculture, Tamaki, Mie 519-0423, Japan
2 Tottori Prefectural Fisheries Experimental Laboratory, Tomari, Tottori 689-0602, Japan