A method for predicting the occurrence of paralytic shellfish poisoning along the coast of Hokkaido in the Okhotsk Sea in summer

To design a method for predicting outbreaks of paralytic shellfish poisoning (PSP) in scallop fishing grounds, the relationship between the distribution of the toxic dinoflagellate Alexandrium tamarense and the dynamics of the Soya Warm Current (SWC) was examined in the Okhotsk Sea off Hokkaido. Surveys were conducted from May to June to clarify the transportation mechanism of A.?tamarense from the oceanic area to the coastal area. The sea-level difference (SLD) between Wakkanai and Abashiri was monitored as an index of the strength of the SWC southeastward flow in an alongshore belt to examine the possible occurrence of A.?tamarense in the coastal area during temporal weakening of the SWC. A bottom-mounted acoustic Doppler current profiler (ADCP) was used for direct observations of the SWC. The results indicated that PSP occurred when low-salinity water contaminated with A.?tamarense extended to the coast during temporal weakening of the SWC due to a decrease of the SLD. Our results strongly indicate that predictions can be realized by monitoring the decrease of SLD as an index of temporal weakening of the SWC after surveys of the distribution of A.?tamarense in the oceanic area before the period of PSP occurrence.     

Degradation of myofibrils in cultured yellowtail <Emphasis Type="Italic">Seriola quinqueradiata</Emphasis> burnt meat: effects of a myofibril-bound EDTA-sensitive protease

“Burnt meat” is a term used to describe the white (pale, grainy, exudative) muscle of yellowtail or tuna. It (with lightness parameter, L* ≥ 55) was observed after 2 h storage in the suffocate in air (SA) 29°C group and after 4 h storage in the spinal cord destruction (SCD) 29°C group. In the SA 17°C group, burnt meat was also observed after 4 h storage. In contrast, the meat in the SCD 17°C group was normal until after 12 h storage. The myosin heavy chain (MHC) was more degraded than the other myofibrillar proteins, and some protein bands increased in the burnt meat. The protease that leads to the degradation of MHC was investigated using myofibrils from the meat. EDTA completely suppressed the degradation, indicating that a myofibril-bound EDTA-sensitive protease (MBESP) may exist in yellowtail muscle and this caused the degradation of MHC. The optimum pH and temperature of MBESP in yellowtail were 5.0 and 50–60°C, respectively.     

A novel genotyping technique for distinguishing between Flavobacterium psychrophilum isolates virulent and avirulent to ayu, Plecoglossus altivelis altivelis (Temminck & Schlegel)

We developed a simple genotyping method for Flavobacterium psychrophilum for analysing two single nucleotide polymorphisms (SNPs) in the gyrA gene and to distinguish between isolates that are virulent and avirulent to ayu, Plecoglossus altivelis altivelis (Temminck & Schlegel). The genotyping method is an on/off switch assay and is based on the polymerase chain reaction technique with phosphorothioated primers. We classified 232 isolates from four families of fish (i.e. Plecoglossidae, Osmeridae, Cyprinidae and Salmonidae) into four genotypes (G‐C, A‐T, A‐C and G‐T). The G‐C type isolates exhibited strong pathogenicity to ayu, whereas the A‐T and G‐T types did not show any pathogenicity to this species. The A‐C type exhibited no or weak pathogenicity to ayu. These results indicate that genotyping F. psychrophilum isolates with two SNPs from gyrA can clearly distinguish between isolates potentially harmful to ayu (G‐C type) and those that are potentially not harmful or less harmful (A‐C, A‐T and G‐T type). The on/off switch assay provides a quick, simple, and very powerful DNA genotyping technique for F. psychrophilum isolates.     

The first occurrence of leaf mold of tomato caused by races 4.9 and 4.9.11 of <Emphasis Type="Italic">Passalora fulva</Emphasis> (syn. <Emphasis Type="Italic">Fulvia fulva</Emphasis>) in Japan

Tomato leaf mold caused by Passalora fulva was found on two tomato varieties carrying the Cf-9 gene in Japan, in 2007. The isolates obtained from Chiba and Fukushima were identified as race 4.9.11, and those from Gunma were races 4.9 or 4.9.11. This is the first report in Japan of tomato leaf mold caused by P. fulva strains that can overcome the Cf-9 gene.     

Algal growth in an irrigation canal and its effect on flow function

Paddy and Water Environment - In the A irrigation district in Yamagata Prefecture, Japan, a rehabilitation project is being implemented due to the aging of the irrigation facilities;...     

Airborne basidiospores as an inoculum source of <Emphasis Type="Italic">Typhula variabilis</Emphasis> and the effect of hilling on the incidence of Typhula winter rot of carrots

Typhula winter rot on overwintering carrots caused by Typhula variabilis is a newly confirmed disease, and no practical control measure is yet available. To develop a control method, here we researched the infection period of T. variabilis and the time that winter rot appeared on carrots. Using spore traps, we found that basidiospore rain occurred from September to November before snowfall in Memuro, Hokkaido. In addition, carrot leaves collected in autumn had already been infected by T. variabilis. These epidemiological investigations revealed that the pathogen releases basidiospores to infect carrot leaves before snow cover, resulting in root decay under snow. An effective control method was then developed to avoid direct contact of basidiospores of T. variabilis with plant tops by covering the plants with soil in autumn. Thus, the percentage of rotted roots was reduced to about half.     

Stomach Chitinase from Japanese Sardine Sardinops melanostictus: Purification,Characterization, and Molecular Cloning of Chitinase Isozymes with a Long Linker

Fish express two different chitinases, acidic fish chitinase-1 (AFCase-1) and acidic fish chitinase-2 (AFCase-2), in the stomach. AFCase-1 and AFCase-2 have different degradation patterns, as fish efficiently degrade chitin ingested as food. For a comparison with the enzymatic properties and the primary structures of chitinase isozymes obtained previously from the stomach of demersal fish, in this study, we purified chitinase isozymes from the stomach of Japanese sardine Sardinops melanostictus, a surface fish that feeds on plankton, characterized the properties of these isozymes, and cloned the cDNAs encoding chitinases. We also predicted 3D structure models using the primary structures of S. melanostictus stomach chitinases. Two chitinase isozymes, SmeChiA (45 kDa) and SmeChiB (56 kDa), were purified from the stomach of S. melanostictus. Moreover, two cDNAs, SmeChi-1 encoding SmeChiA, and SmeChi-2 encoding SmeChiB were cloned. The linker regions of the deduced amino acid sequences of SmeChi-1 and SmeChi-2 (SmeChi-1 and SmeChi-2) are the longest among the fish stomach chitinases. In the cleavage pattern groups toward short substrates and the phylogenetic tree analysis, SmeChi-1 and SmeChi-2 were classified into AFCase-1 and AFCase-2, respectively. SmeChi-1 and SmeChi-2 had catalytic domains that consisted of a TIM-barrel (β/α)₈–fold structure and a deep substrate-binding cleft. This is the first study showing the 3D structure models of fish stomach chitinases.     

Characterization of feline CD56 molecule expressed on insect cells by the baculovirus expression system.

Recently we cloned 140 kDa form of feline CD56 cDNA. In this study, we expressed the feline CD56 molecule by the baculovirus expression system. We found that the molecule was expressed on the cell surface when examined by the indirect immunofluorescence assay using an anti-human CD56 monoclonal antibody. Immunoblotting analysis revealed that the molecular weight of the major expressed product was 140 kDa. Interestingly we found that the insect cells expressing the feline CD56 molecule aggregated, indicating that the expressed molecule mediates homophilic adhesion.     

Studies on the inhibition of methanogenesis and dechlorination by (4-hydroxyphenyl) chloromethanesulfonate

The purpose of this study was to demonstrate the inhibitory effect of chemicals on methane emissions in paddy soil. We found that (4-hydroxyphenyl) chloromethanesulfonate (C-1) has a methanogenic inhibition activity, and we studied its inhibition mechanism using laboratory tests. The study found that C-1 treatment of flooded soil did not significantly affect the bacterial community but rather the archaeal community; particularly, Methanosarcina spp. C-1 strongly inhibited the aceticlastic methanogenesis route. It was suggested that the inhibitory target of C-1 was different from the well-known methanogenic inhibitor 2-bromoethanesulfonate, which targets methyl-coenzyme M reductase of methanogen. In addition, C-1 had a secondary effect of inhibiting the dechlorination of chlorophenols. Although field trials are required as the next development step, C-1 can be used to reduce methane emissions from paddy fields, one of the largest sources in the agricultural sector.