New Leaf Spot Disease of Cymbidium Species Caused by Fusarium subglutinans and Fusarium proliferatum

Fusarium species were consistently isolated from yellow, swollen spots with reddishbrown centers and small black spots on leaves of Cymbidium plants in the greenhouse. Fusarium subglutinans caused the yellow spots and Fusarium proliferatum caused either the yellow or the black spots. We propose the name “yellow spot” for the new disease. To denote differences in their pathogenicity to orchid plants, we designate the population causing yellow spot as race Y and that causing black spot as race B of F. proliferatum. Received 29 October 1999/ Accepted in revised form 10 March 2000     

Field Distribution of END Phenomenon-Negative Bovine Viral Diarrhea Virus

Field isolates of BVDV which do not show the exaltation of Newcastle disease virus (END) phenomenon (END^–) are rarely reported. In this study, 45 BVDV field isolates from cattle in Hokkaido prefecture in Japan were analyzed by the reverse plaque formation method, the END method and observation of cytopathic effects. END^– virus was detected in 34 of 45 isolates (75.6%), although 35 of 45 field isolates contained END phenomenon positive virus as the predominant virus population. We propose that END^– viruses are widely distributed in the field and that it is possible that the mixture of biologically distinct BVDV correlates with the appearance of disease in infected animals.     

Environmental determinants of growth rates for larval Japanese anchovy Engraulis japonicus in different waters

Do disparate mechanisms determine growth rates of fish larvae in the different regions? The relationship between growth rates and environmental factors (sea temperature and food availability) was examined for larval Japanese anchovy Engraulis japonicus in geographically and environmentally different waters, through sagittal otolith microstructure analysis. Recent 3‐day mean growth rates directly before capture were positively related with sea‐surface temperature (SST) but not with food availability (plankton density) for the larvae in the Kuroshio Extension and Kuroshio–Oyashio transition regions of the western North Pacific. On the contrary, variations in recent growth rates were attributed to food availability (plankton density) as well as SST for the larvae in the East China Sea. In the shirasu fishing ground in Sagami Bay, larval growth rates were variable under the influences of both SST and food availability (feeding incidence). On the surface, the growth–environment relationships seemed to differ among regions. However, a definite general pattern of the dome‐shaped relationship between recent growth rates and SST was observed when all the regions were combined. Growth rates were similar even among clearly different regions if at the same SST. Overall, growth rates roughly increased with SST until they reached the maximum at SST of 21–22°C (i.e. optimal growth temperature), and declined when SST went over 21–22°C. On the contrary, no clear relationship was observed between growth rate and plankton density or between SST and plankton density. Therefore, the apparent among‐region differences would be firstly caused by the differences in regional SST range. The systematic mechanism of growth determination for widespread pelagic fish species larvae would be run by primarily sea temperature and secondarily food availability, at the species level.     

Acoustic observations of fish schools and scattering layers in a Kuroshio warm-core ring and its environs

Biological sound scattering characteristics in a frontal region between warm and cold waters were examined at the southern edge of a Kuroshio warm-core ring off Sanriku, the northeast coast of Japan. The scattering strength was low in the surrounding cold water and high in the warm-core ring. The depth and thickness of sound-scattering layers changed in accordance with the vertical structure of the water mass during the day or at night. Intense, thick scattering layers were observed on the warm-water side of the front and farther inside the warm-core ring. Fish schools were distributed in the mixed layer warmer than 17°C at depths of 10-30m above the scattering layers on the warm-water side of the front.     

Serotyping of Vibrio anguillarum isolated from diseased freshwater fish in Japan

Abstract. During the period from 1965 to 1980, 263 Vibrio anguillarum strains from ayu, Plecoglossiis altivelis (Temminck & Schlegel), two from rainbow trout. Salmo gairdneri Richardson, and two from eel, Anguilla japonica (Temminck & Schlegel), were collected from fish suffering from vibriosis in various parts of Japan. On the basis of cross-agglutination and cross-absorption tests with thermostable (O) antigens, six distinct serotypes (A, B, C, D, E and F) were established among 12 selected strains of V. anguillarum . 241 strains isolated from ayu and two strains from rainbow trout belonged to serotype A, six strains from ayu and one strain from eel to serotype B, 12 strains from ayu to serotype C, three strains from ayu to serotype D, one strain from ayu to serotype E, and one strain from eel to serotype F. V. anguillarum strains belonging to serotypes D, E and F have not been detected from ayu, rainbow trout and eel since 1973; these serotypes appear to be minor types. V. anguillarum strain NCMB 6 and 1669 belong to our serotype A and V. anguillarum 813 to our serotype C.     

Cloning and characterization of the haemolysin determinants from Aeromonas hydrophila

Abstract. Two haemolysin genes (AHH4 and AHH-2) of Aeromonas hydrophila ATCC7966 were cloned into a plasmid vector in Escherichia coli K-12. An open reading frame (ORF) of the AHH-1 haemolysin gene was 1734 base pairs (bp). and corresponded to a protein of 577 amino acid residues. Analysis of the deduced amino sequence indicated a highly hydrophobic N-terminal region which had the characteristics of a leader peptide. The sequence also included the -10 region and the -35 region of a promoter, and a ribosome- binding site upstream from the ORF. The termination site was located downstream from the ORF. The haemolysin was a thermolabile protein with the predicted molecular mass of 60 kDa. The AHH-1 gene is distributed in various A. hydrophila and A. salmonicida strains. The nucleotide sequence of a 981 bp ORF of the AHH-2 gene was encoded with the predicted molecular mass of 377 kDa polypeptides. The homology of the nucleotide sequence was very low between the AHH-1 and AHH-2 genes, and also with the aerolysin gene cloned by Howard & Buckley (19S6). No leader peptide was found in the N-terminal region of the ORF of the AHH2 gene. The AHH-2 gene was detected in the original strain ATCC7966, but was not detected in other tested strains of A. hydrophila and A. salmonicida.     

Feasibility of radial and circumferential strain analysis using 2D speckle tracking echocardiography in cats

The purpose of the present study is to investigate the feasibility of strain analysis using speckle tracking echocardiography (STE) in cats and to evaluate STE variables in cats with hypertrophic cardiomyopathy (HCM). Sixteen clinically healthy cats and 17 cats with HCM were used. Radial and circumferential strain and strain rate variables in healthy cats were measured using STE to assess the feasibility. Comparisons of global strain and strain variables between healthy cats and cats with HCM were performed. Segmental assessments of left ventricle (LV) wall for strain and strain rate variables in cats with HCM were also performed. As a result, technically adequate images were obtained in 97.6% of the segments for STE analysis. Sedation using buprenorphine and acepromazine did not affect any global strain nor strain rate variable. In LV segments of cats with HCM, reduced segmental radial strain and strain rate variables had significantly related with segmental LV hypertrophy. It is concluded that STE analysis using short axis images of LV appeared to be clinically feasible in cats, having the possibility to be useful for detecting myocardial dysfunctions in cats with diseased heart.