Masahiro Sakai

Immunomodulatory effects of the fermented products of chicken egg, EF203, on rainbow trout, Oncorhynchus mykiss

Abstract Immunomodulatory effects of immunoactive peptides from the fermented products of chicken egg (EF203) administered orally to rainbow trout, Oncorhynchus mykiss , were investigated. The chemiluminescent responses of kidney phagocytes after treatment with EF203 were significantly increased. Fish administered EF203 showed high phagocytic activities as compared to controls, and immunomodulatory effects were found to be dose dependent. Fish treated with EF203 displayed an increased resistance to both natural and experimental beta-haemolytic streptococcal infection.

Purification and characterization of an antibacterial and antineoplastic protein secretion of a sea hare, Aplysia juliana

The fetid secretion of a sea hare, Aplysia juliana, was lethal to crabs and also inhibited the growth of bacteria. When the secretion was partitioned between water and n-hexane, only the n-hexane layer, which had a nauseating odor, was lethal to crabs. The water-soluble fraction showed strong antibacterial activity and inhibited the growth of both Gram-positive and Gram-negative bacteria. Antibacterial activity of the water-soluble fraction was destroyed by heating at 50 degrees C for 15 min, but was resistant to treatment with proteolytic enzymes. The active principle, named julianin-S, was purified by gel filtration and ion exchange chromatography. The purified specimen gave a single protein showing a mol. wt of approximately 67,000, as determined by gel filtration. Julianin-S inhibited the growth of Bacillus subtilis by 50% at a concentration of 70 ng protein/ml. It was also cytotoxic to murine tumor cells and inhibited in vitro growth of L1210 cells by 50% at a concentration of 8 ng protein/ml.

Lectins in the hemolymph of a starfish, Asterina pectinifera: Purification and characterization

Naturally occurring lectins or receptorspecific proteins have been reported in the hemolymph and various tissue extracts of marine invertebrates (1,2). There has been extensive discussion on the physiological significance of lectins. In the case of invertebrate humoral lectins, it has been postulated that one of their physiological functions is recognition of self from nonself in cooperation with cellular and humoral defense processes such as vertebrate antibodies (3,4). The presence of multiple lectins in the hemolymph in the arthropods and mollusks (5-9) is one piece of important evidence in support of the hypothesis that considers the lectins to be recognition factors in defense procedures since it is not readily acceptable that only single molecular species of lectin distinguish nonself from self. The opsonizing effects of humoral lectins or cell membrane-associated lectins have also been demonstrated in mollusks and arthropods (10-14). In the course of our screening for lectins in marine invertebrates, we observed the presence of lectins that agglutinated mammal erythrocytes and a marine bacterium in the hemolymph of a starfish, Asterina pectinifera. An attempt was made to purify the active components from the hemolymph. The present article deals with the agglutinating activity of the starfish hemolymph and the properties of a lectin, APL-R, that preferentially agglutinated rabbit erythrocytes from A. pectinifera hemolymph.

Comparison of Methods Used to Detect Renibacterium salmoninarum, the Causative Agent of Bacterial Kidney Disease

Abstract Various diagnostic methods used to detect Renibacterum salmoninarum, the causative agent of bacterial kidney disease (BKD), were compared. The most sensitive method was the enzyme immunoassay (the indirect dot blot assay), which could detect 102 bacterial cells per gram of kidney tissue. The minimum bacteria concentrations showing positive reactions to the indirect fluorescent antibody test (IFAT) and the coagglutination test were 103 and 104 cells/g kidney, respectively. The sensitivities of the Gram stain, immunodiffusion procedure, and latex agglutination test were low, and these methods could only be applied to fish with overt BKD symptoms. Altogether, 656 coho salmon Oncorhynchus kisutch were examined for R. salmoninarum antigen with the direct and indirect dot blot assays (DDBA and IDBA) and the IFAT. Among the fish sampled, positive reactions were obtained in 11.8% by the DDBA, 28.2% by the IDBA, and 12.9% by the IFAT.

The immune response of rainbow trout (Oncorhynchus mykiss) injected with five Renibacterium salmoninarum bacterins

Abstract Five bacterins consisting of formalin-killed, heat-killed, pH-lysed, Streptococcus bacterin (formalin-killed cells)-mixed, or ultraviolet (UV)-killed cells of Renibacterium salmoninarum were tested for the immune responses elicited in rainbow trout (Oncorhynchus mykiss). Low levels of agglutinating antibody titres were formed in vaccinated fish and in some fish these were undetectable. Phagocytosis was significantly increased in vaccinated fish, except with the Streptococcus-mixed bacterin, and the chemiluminescent responses of leucocytes were stimulated only with the pH-lysed and UV-killed bacterins. However, no significant protection was observed in the fish when they were experimentally challenged.