Mercury levels of small fishes: influence of size and catch area

In the present study, we assessed small fishes as potential feed fishes with the lowest mercury levels. The mercury levels of four small pelagic fishes and a benthic fish from the Pacific Ocean and the Sea of Japan, i.e., spotted chub mackerel Scomber australasicus, chub mackerel Scomber japonicus, horse mackerel Trachurus trachurus, round scad Decapterus punctatus, and bastard halibut Paralichthys olivaceus, were determined. Total mercury levels in fish muscle were measured using a reduction vaporizing atomic absorption method. There were no significant correlations between body weight and mercury levels for these species. However, significant differences were observed in the mercury levels of these species between the two catch locations, with fish caught in the Pacific Ocean having higher mercury levels. This difference may be due to the Pacific Ring of Fire, a highly seismically and volcanically active zone, which is located in the Pacific Ocean. Preference for these fishes for use in aquaculture should refer to the area where they are caught in addition to the species.     

Green tea consumption in everyday life and mental health

OBJECTIVE: Green tea has been widely acknowledged in Japan to induce a pleasurable mental feeling. Recent laboratory studies have suggested positive psychological effects as a result of consuming green tea. The present study examined whether green tea consumption in everyday life in Japan is associated with positive mental health. DESIGN: A cross-sectional study was performed in February-March 2002. SETTING AND SUBJECTS: The subjects of the study consisted of a general population of 600 Japanese aged 20-69 years. Responses of 380 subjects, obtained by home-visit interview, were analysed. The questionnaire inquired about consumption of brewed green tea and other beverages, perceived mental health status, lifestyle and others. The 12-item General Health Questionnaire (GHQ 12) was used for the assessment of mental ill-health (GHQ score >or=4). RESULTS: After adjustments for age, area, perceived mental stress, lifestyle and daily caffeine intake, the consumption of brewed green tea was not statistically associated with any decrease in risk of mental ill-health among either males or females (odds ratio (OR)=0.78, 95% confidence interval (CI)=0.47-1.29 for males; OR=0.77, 95% CI=0.51-1.14 for females). Daily caffeine intake (100 mg) inclusive of green tea, black tea, coffee and other caffeine-containing beverages was associated with a higher risk of mental ill-health among females (OR=1.26, 95% CI=1.01-1.56). CONCLUSIONS: The results provide population-based evidence on the consumption of brewed green tea in everyday life and mental health, together with information on consumption patterns of various beverages and lifestyles.     

Genetic characterization and gonad development of artificially produced interspecific hybrids of the abalones, Haliotis discus discus Reeve, Haliotis gigantea Gmelin and Haliotis madaka Habe

Hybridization among abalone species has been suggested as a possible means to increase their growth rates for aquaculture. As a first step to test the usefulness of the hybrids of Japanese abalone species (Haliotis discus discus, Haliotis gigantea and Haliotis madaka) for aquaculture, we characterized the genetic background and gonad development of hybrids that were produced by artificial insemination. The hybrid status of the resulting offspring was confirmed by assaying 14 allozymes and by RFLP analysis of the 16s rRNA and cytochrome oxidase I (COI) regions of mtDNA using 13 restriction enzymes. Histological examination of the gonads of the hybrids was conducted in comparison with those of the parental species. Cross‐breeding among the three species was conducted successfully in all combinations although with lower fertilization rates (means of 1.3–60.8%) than the parental species (34.3–90%). Crosses between H. discus discus and H. madaka had higher fertilization rates (22.4–60.8%) than those involving H. gigantea (1.3–19.9%). The hybrids were ascertained by the presence of both parental genotypes at the LDH‐A, ME‐A, MDH‐A and GPI loci. The maternal origin of the hybrid mtDNA was confirmed by digestion with DdeI, TaqI, HpaII of the COI region. No polymorphism was observed in the 16S rRNA region. The hybrids had gonadal development and maturity stages similar to the parental species up to fully mature oocytes and sperm. They spawned upon stimulation and produced viable offspring with high fertilization rates and successful development to the juvenile stage in back‐ and homologous hybrid crosses.     

Normalization method for canopy temperature as an indirect indicator of yield potential in wheat breeding programs

Canopy temperature (CT) is often related to potential yield and is a possible yield indicator in breeding programs. However, it is difficult to evaluate genetic variations of CT accurately in large-scale investigations, such as breeding programs, because CT is strongly affected by environmental conditions. In this study, to precisely evaluate these genetic variations, we determined the environmental factors that affect CT measurement and proposed a convenient normalization method to minimize their influence. We measured the CT of CT-high or CT-low cultivars in the field under various conditions. We found that as the sun and shade levels were alternated, the CT changed within seconds; the position in the field also critically affected the CT. However, even under these conditions, the differences between cultivars became clearer if CT was normalized by neighboring lines. Additionally, we revealed that CT measurements between 12:00 and 15:00 maximized the difference between cultivars. Using our normalization technique under the favorable conditions specified can help breeders select high-yield lines using CT in breeding programs.     

Race 3, a new race of<Emphasis Type="Italic"> Fusarium oxysporum</Emphasis> f. sp. <Emphasis Type="Italic">lactucae </Emphasis>determined by a differential system with commercial cultivars

 Pathogenic variation among 26 Japanese isolates of Fusarium oxysporum f. sp. lactucae (FOL) was tested using 21 lettuce cultivars to select commercial lettuce cultivars as race differential indicators. Cultivar Costa Rica No. 4 was resistant to race 1 but susceptible to race 2, consistent with the conventional standard differential line VP1010. Cultivar Banchu Red Fire was susceptible to race 1 but resistant to race 2, which showed an opposite type of reaction as another differential line VP1013. Cultivar Patriot was susceptible to both races. The resistance reactions of the three cultivars under field conditions were identical with that observed in the seedlings. Thus cv. Costa Rica No. 4 and cv. Banchu Red Fire can be used as differential hosts to identify pathogenic races of FOL. This differential system showed that all FOL isolates obtained from diseased butterhead lettuce in Fukuoka, Japan were new races (i.e., pathogenic to three cultivars). We propose that the new race be designated race 3. Isolates of FOL, the pathogen of Fusarium wilt in lettuce, obtained from California showed the same reaction as that of race 1. Furthermore, the Japanese isolate SB1-1 (race 1) and California isolate HL-2 belonged to the same vegetative compatibility group. Our results suggest that both of the fungi are the same forma specialis. Received: March 25, 2002 / Accepted: August 26, 2002     

The Complete Nucleotide Sequence of Potato virus X Strain OS: The First Complete Sequence of a Japanese Isolate

The complete nucleotide sequence of the genomic RNA of a Japanese isolate of Potato virus X (PVX), strain OS (PVX-OS), was determined. The PVX-OS genome is 6435 nucleotides in length, excluding the 3′ poly(A) sequence, and encodes for five open reading frames (ORFs), similar to other reported PVX strains. Comparisons of the nucleotide sequence of PVX-OS with those of European and South American PVX strains revealed that the PVX-OS genomic sequence showed 95-96% homology with European strains and 77-78% with South American strains. Phylogenetic analysis of PVX-OS and other PVX strains found that PVX-OS clusters with European strains. This is the first report on the complete nucleotide sequence of a PVX strain from Japan. Received 10 May 2001/ Accepted in revised form 26 October 2001     

Gene Arrangement and Sequence of str Operon of Phytoplasma Resemble Those of Bacillus More Than Those of Mycoplasma

The complete region of a putative streptomycin operon (str operon) of onion yellows (OY) phytoplasma, a phytopathogenic mollicute, was isolated and sequenced. This operon contains four genes, rps12, rps7, fus, and tuf, encoding ribosomal proteins S12 and s7, elongation factor (EF) -G, and EF-Tu, respectively. These four genes constitute the str operon in non-mollicute bacteria, such as Escherichia coli and Bacillus subtilis. In two species of mollicute Mycoplasma, the tuf gene was reported not to be included in this operon, but was located apart, indicating that the gene arrangement of this operon in phytoplasmas resembles that of B. subtilis more than that of Mycoplasma spp. In addition, the deduced amino acid sequence of EF-G of phytoplasmas also resembles that of B. subtilis more than that of Mycoplasma spp. These results suggest that analyses of the gene organization and sequence of the phytoplasma genome will provide valuable insights into evolutionary relationships among the culturable mollicutes, phytoplasmas and other Gram-positive bacteria. Received 25 April 2001/ Accepted in revised form 21 August 2001     

Effect of an Introduced Phytoene Synthase Gene Expression on Carotenoid Biosynthesis in the Marine Diatom Phaeodactylum tricornutum

Carotenoids exert beneficial effects on human health through their excellent antioxidant activity. To increase carotenoid productivity in the marine Pennales Phaeodactylum tricornutum, we genetically engineered the phytoene synthase gene (psy) to improve expression because RNA-sequencing analysis has suggested that the expression level of psy is lower than other enzyme-encoding genes that are involved in the carotenoid biosynthetic pathway. We isolated psy from P. tricornutum, and this gene was fused with the enhanced green fluorescent protein gene to detect psy expression. After transformation using the microparticle bombardment technique, we obtained several P. tricornutum transformants and confirmed psy expression in their plastids. We investigated the amounts of PSY mRNA and carotenoids, such as fucoxanthin and β-carotene, at different growth phases. The introduction of psy increased the fucoxanthin content of a transformants by approximately 1.45-fold relative to the levels in the wild-type diatom. However, some transformants failed to show a significant increase in the carotenoid content relative to that of the wild-type diatom. We also found that the amount of PSY mRNA at log phase might contribute to the increase in carotenoids in the transformants at stationary phase.     

Seasonal characteristics of surface water quality in the wastewater catchment system of an urbanizing basin

Vientiane, Lao PDR, has been subject to extensive and ongoing urbanization plans, including development of natural marshes and residentialization of paddy fields into suburban areas, despite natural marshes playing a vital role in treating wastewater from urban areas. Therefore, it is important to understand the current situation regarding the nutrient balance in these natural wastewater treatment systems to predict future conditions and design appropriate measures against water quality deterioration. However, limited data are available in Vientiane on the hydrological characteristics of water and nutrient runoff that flow into marshes through drainage canals. In this study, we conducted a periodic survey of drainage canals and Mak Hiao River in the wastewater catchment system surrounding Vientiane during the rainy and dry seasons. We monitored the discharge of surface water at 21 observation sites and analyzed water quality of nitrogen, phosphorus, and total organic carbon. These observations revealed that the concentrations of dissolved nitrogen and phosphorus were significantly higher at sites in urban areas, followed by sites in the main river basin and those in agricultural areas. Dissolved nitrogen and phosphorus concentrations varied with runoff discharge, especially in urban and river basin sites, with lower concentrations in the rainy season and higher concentrations in the dry season. On the other hand, we found no significant differences between the rainy and dry seasons in nutrient concentrations in the agricultural basin. Finally, we proposed measures to counteract the deterioration of water quality during dry seasons and simulated the impact of these measures.     

Functional insulin‐like factor 3 (INSL3) hormone‐receptor system in the testes and spermatozoa of domestic ruminants and its potential as a predictor of sire fertility

Insulin‐like factor 3 (INSL3) is essential for fetal testis descent, and has been implicated in the testicular and sperm functions in adult males; however, similar functions in domestic ruminants remain largely unknown. This study investigated the functional INSL3 hormone‐receptor system in adult ruminant testes and spermatozoa, and explored its potential to diagnose the fertility of sires. Testes and spermatozoa were obtained from fertile bulls, rams and he‐goats, whereas subfertile testes and spermatozoa were obtained only from bulls. As expected, INSL3 was visualized in Leydig cells, while we clearly demonstrated that the functional receptor, relaxin family peptide receptor 2 (RXFP2), enabling INSL3 to bind was identified in testicular germ cells and in the sperm equatorial segment of bulls, rams and he‐goats. In comparison to fertile bulls, the percentage of INSL3‐ and RXFP2‐expressing cells and their expression levels per cell were significantly reduced in the testes of subfertile bulls. In addition, the population of INSL3‐binding spermatozoa was also significantly reduced in the semen of subfertile bulls. These results provide evidence for a functional INSL3 hormone‐receptor system operating in ruminant testes and spermatozoa, and its potential to predict subfertility in sires.