Assessment of the nutritional status of field-caught larval Pacific bluefin tuna by RNA/DNA ratio based on a starvation experiment of hatchery-reared fish

RNA/DNA ratio is a useful and reliable indicator of the nutritional status of fish larvae and juveniles. In order to assess the nutritional status of field-caught larval Pacific bluefin tuna Thunnus orientalis (Temminck et Schlegel), starvation experiments of hatchery-reared larvae were conducted and changes in the RNA/DNA ratio of fed and starved larvae were analyzed. Starvation experiments were conducted every 3 days after first feeding. The survival rate of Pacific bluefin tuna larvae ranged 10-50% after 1 day of starved conditions and growth retardation was observed immediately. These results suggest that Pacific bluefin tuna larvae have a very low tolerance to starvation. The RNA/DNA ratios of fed larvae were approximately 2.0-4.0. On the other hand, the value of starved larvae significantly decreased to 1.0-3.0. The nutritional status of 3 cohorts of field-caught tuna larvae collected in the northwestern Pacific Ocean was examined based on the value of the RNA/DNA ratio of the 1 day starved larvae. 4.35-25.77% of the cohorts were regarded as the “starving condition”, which was negatively correlated to the ambient prey densities. These findings suggest that the nutritional condition of larval Pacific bluefin tuna was influenced by the ambient prey density, and starvation itself and starvation-induced predation could greatly contribute to mortality in the larval period of Pacific bluefin tuna.     

Whole-genome sequencing and analysis of the Malaysian cynomolgus macaque (Macaca fascicularis) genome

ABSTRACT: BACKGROUND: The genetic background of the cynomolgus macaque (Macaca fascicularis) is made complex by the high genetic diversity, population structure, and gene introgression from the closely related rhesus macaque (Macaca mulatta). Herein we report the whole-genome sequence of a Malaysian cynomolgus macaque male with more than 40-fold coverage, which was determined using a resequencing method based on the Indian rhesus macaque genome. RESULTS: We identified approximately 9.7 million single nucleotide variants (SNVs) between the Malaysian cynomolgus and the Indian rhesus macaque genomes. Compared with humans, a smaller nonsynonymous/synonymous SNV ratio in the cynomolgus macaque suggests more effective removal of slightly deleterious mutations. Comparison of two cynomolgus (Malaysian and Vietnamese) and two rhesus (Indian and Chinese) macaque genomes, including previously published macaque genomes, suggests that Indochinese cynomolgus macaques have been more affected by gene introgression from rhesus macaques. We further identified 60 nonsynonymous SNVs that completely differentiated the cynomolgus and rhesus macaque genomes, and that could be important candidate variants for determining species-specific responses to drugs and pathogens. The demographic inference using the genome sequence data revealed that Malaysian cynomolgus macaques have experienced at least three population bottlenecks. CONCLUSIONS: This list of whole-genome SNVs will be useful for many future applications, such as an array-based genotyping system for macaque individuals. High-quality whole-genome sequencing of the cynomolgus macaque genome may aid studies on finding genetic differences that are responsible for phenotypic diversity in macaques and may help control genetic backgrounds among individuals.     

Effect of sustained limb ischemia on norepinephrine release from skeletal muscle sympathetic nerve endings

Acute ischemia has been reported to impair sympathetic outflow distal to the ischemic area in various organs, whereas relatively little is known about this phenomenon in skeletal muscle. We examined how acute ischemia affects norepinephrine (NE) release at skeletal muscle sympathetic nerve endings. We implanted a dialysis probe into the adductor muscle in anesthetized rabbits and measured dialysate NE levels as an index of skeletal muscle interstitial NE levels. Regional ischemia was introduced by microsphere injection and ligation of the common iliac artery. The time courses of dialysate NE levels were examined during prolonged ischemia. Ischemia induced a decrease in the dialysate NE level (from 19+/-4 to 2.0+/-0 pg/ml, mean+/-S.E.), and then a progressive increase in the dialysate NE level. The increment in the dialysate NE level was examined with local administration of desipramine (DMI, a membrane NE transport inhibitor), omega-conotoxin GVIA (CTX, an N-type Ca(2+) channel blocker), or TMB-8 (an intracellular Ca(2+) antagonist). At 4h ischemia, the increment in the dialysate NE level (vehicle group, 143+/-30 pg/ml) was suppressed by TMB-8 (25+/-5 pg/ml) but not by DMI (128+/-10 pg/ml) or CTX (122+/-18 pg/ml). At 6h ischemia, the increment in the dialysate NE level was not suppressed by the pretreatment. Ischemia induced biphasic responses in the skeletal muscle. Initial reduction of NE release may be mediated by an impairment of axonal conduction and/or NE release function, while in the later phase, the skeletal muscle ischemia-induced NE release was partly attributable to exocytosis via intracellular Ca(2+) overload rather than opening of calcium channels or carrier mediated outward transport of NE.     

The life cycle of Hymenoscyphus fraxineus on Manchurian ash,Fraxinus mandshurica,in Japan

Hymenoscyphus fraxineus causes a lethal disease known as “ash dieback” in the common ash, Fraxinus excelsior, in Europe. It is hypothesized that the fungus originated from East Asia. This fungus is found on the leaf litter of the Manchurian ash, Fraxinus mandshurica, in Japan and is reported to produce apothecia on pseudosclerotial plates formed mainly on decomposing rachises. However, dieback disease has not been reported in Japan, and little is known about the life cycle of H. fraxineus. This study was conducted to explore the behavior and life cycle of this fungus. It was revealed that, after infection by ascospores, H. fraxineus endophytically inhabits the living leaves of F. mandshurica. On fallen leaves, the fungus behaves saprophytically, producing apothecia on pseudosclerotial plates formed mainly on the decomposing rachises. Analysis by real-time quantitative polymerase chain reaction (qPCR) revealed that the amount of H. fraxineus DNA sharply increased in rachises, while such sharp increase of DNA was not found in leaflets.     

PDK1 is required for the hormonal signaling pathway leading to meiotic resumption in starfish oocytes

Meiotic resumption is generally under the control of an extracellular maturation-inducing hormone. It is equivalent to the G2-M phase transition in somatic cell mitosis and is regulated by cyclin B-Cdc2 kinase. However, the complete signaling pathway from the hormone to cyclin B-Cdc2 is yet unclear in any organism. A model system to analyze meiotic resumption is the starfish oocyte, in which Akt/protein kinase B (PKB) plays a key mediator in hormonal signaling that leads to cyclin B-Cdc2 activation. Here we show in starfish oocytes that when PDK1 activity is inhibited by a neutralizing antibody, maturation-inducing hormone fails to induce cyclin B-Cdc2 activation at the meiotic G2-M phase transition, even though PDK2 activity becomes detectable. These observations assign a novel role to PDK1 for a hormonal signaling intermediate toward meiotic resumption. They further support that PDK2 is a molecule distinct from PDK1 and Akt, and that PDK2 activity is not sufficient for the full activation of Akt in the absence of PDK1 activity.     

Characterization of Methanosarcina mazeii TMA isolated from a paddy field soil

We isolated a methanogenic strain, designated as strain TMA (=DSM 9195), from an enrichment culture inoculated with a Japanese paddy field soil. Strain TMA was Gram positive and strictly anaerobic. Cell shape was pseudosarcina-like, and cells were nonmotile. The strain was able to use methylamines, methanol, H₂–CO₂, and acetate as substrates for methanogenesis, but did not utilize formate. The optimum temperature and optimum pH were 30–37°C and 6.5–7.5 respectively. The G+C content of the DNA was 42.1 mol %. Strain TMA had DNA-DNA hybridization values of more than 80% with Methanosarcina mazeii S-6^T (T = type strain). On the basis of phenotypic and genotypic characteristics, we identified strain TMA as M. mazeii. This is the first methylotrophic methanogen isolated from a paddy field soil and identified to the species level.     

FCGR3A-158 polymorphism influences the biological response to infliximab in Crohn’s disease through affecting the ADCC activity

An association between FCGR3A-158 V/F polymorphism and biological responses to infliximab has been reported in Crohn’s disease (CD) in Western countries. However, little is known about the mechanism by which gene polymorphism affects the responses to infliximab. The aims of this study were to confirm the association in Japanese CD patients and to reveal the effect of gene polymorphism on biological responses to infliximab. Japanese CD patients were examined retrospectively at weeks 8 and 30. Clinical and biological responses were assessed by the Crohn’s disease activity index and C-reactive protein levels, respectively. The infliximab-binding affinity of natural killer (NK) cells from FCGR3A-158 V/V, V/F and F/F donors was examined. Infliximab-mediated antibody-dependent cell-mediated cytotoxicity (ADCC) activities were also determined using transmembrane TNF-α-expressing Jurkat T cells as target cells and peripheral blood mononuclear cells (PBMCs) from V/V, V/F and F/F donors as effector cells. Biological responses at week 8 were statistically higher in V/V patients, whereas no significant differences were observed in either clinical responses at weeks 8 and 30 or biological responses at week 30 among the three genotypes. NK cells and PBMCs from V/V patients also showed higher infliximab-binding affinity and infliximab-mediated ADCC activity, respectively. Our results suggest that FCGR3A-158 polymorphism is a predicting factor of biological responses to infliximab in the early phases. FCGR3A-158 polymorphism was also found to affect the infliximab-binding affinity of NK cells and infliximab-mediated ADCC activity in vitro, suggesting that an effect on ADCC activity influences biological responses to infliximab in CD patients.