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Search Results: 1 - 10 of 1122 matches for " Hideyuki Doi "
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Stream grazers determine their crawling direction on the basis of chemical and visual/tactile microalgal cues
Izumi Katano,Hideyuki Doi
PeerJ , 2015, DOI: 10.7287/peerj.preprints.350v1
Abstract: This study aimed to determine the association of herbivore behavior with cues from producers. We used stream grazer Glossosoma larvae and determined their crawling direction in relation to the chemical and visual cues from microalgae. The experimental treatments included control (no cue), particulate (chemical and visual/tactile cues), and dissolved (chemical cue) cues from microalgae. The experimental water samples were randomly placed into either arms of a Y-shaped channel, and the crawling direction of the grazers was determined. Although the grazers crawled toward the arm containing either particulate or dissolved cues, they preferred the arm with particulate cues. This suggested that grazers responded well when both visual/tactile (i.e., drifting algal cells) and chemical cues (algal smell) were present, and that visual/tactile cues were more important for foraging. In natural habitats, grazers detect cues from both producers and predators and use them to maximize fitness by avoiding predation and obtaining food.
Stream grazers determine their crawling direction on the basis of chemical and particulate microalgal cues
Izumi Katano,Hideyuki Doi
PeerJ , 2015, DOI: 10.7717/peerj.503
Abstract: This study aimed to determine the association between herbivore behavior and cues from producers. We used stream grazer Glossosoma larvae and determined their crawling direction in relation to chemical and visual cues from microalgae. The experimental treatments included control (no cue), particulate (chemical and particulate cues), and dissolved (chemical cue) cues from microalgae. The experimental water samples were randomly placed into either arm of a Y-shaped channel, and the crawling direction of the grazers was determined. Although the grazers crawled toward the arm containing either particulate or dissolved cues, they preferred the arm with particulate cues. This suggested that grazers responded well to both particulate (i.e., drifting algal cells) and chemical (algal smell) cues, and that particulate cues were more important for foraging. In natural habitats, grazers detect cues from producers and change their behaviors to maintain a balance between top-down and bottom-up cues.
Trophic Position and Metabolic Rate Predict the Long-Term Decay Process of Radioactive Cesium in Fish: A Meta-Analysis
Hideyuki Doi,Teruhiko Takahara,Kazuya Tanaka
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0029295
Abstract: Understanding the long-term behavior of radionuclides in organisms is important for estimating possible associated risks to human beings and ecosystems. As radioactive cesium (137Cs) can be accumulated in organisms and has a long physical half-life, it is very important to understand its long-term decay in organisms; however, the underlying mechanisms determining the decay process are little known. We performed a meta-analysis to collect published data on the long-term 137Cs decay process in fish species to estimate biological (metabolic rate) and ecological (trophic position, habitat, and diet type) influences on this process. From the linear mixed models, we found that 1) trophic position could predict the day of maximum 137Cs activity concentration in fish; and 2) the metabolic rate of the fish species and environmental water temperature could predict ecological half-lives and decay rates for fish species. These findings revealed that ecological and biological traits are important to predict the long-term decay process of 137Cs activity concentration in fish.
Using Environmental DNA to Estimate the Distribution of an Invasive Fish Species in Ponds
Teruhiko Takahara, Toshifumi Minamoto, Hideyuki Doi
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0056584
Abstract: Knowledge of the presence of an invasive species is critical to monitoring the sustainability of communities and ecosystems. Environmental DNA (eDNA), DNA fragments that are likely to be bound to organic matters in the water or in shed cells, has been used to monitor the presence of aquatic animals. Using an eDNA-based method, we estimated the presence of the invasive bluegill sunfish, Lepomis macrochirus, in 70 ponds located in seven locales on the Japanese mainland and on surrounding islands. We quantified the concentration of DNA copies in a 1 L water sample using quantitative real-time polymerase chain reaction (qPCR) with a primer/probe set. In addition, we visually observed the bluegill presence in the ponds from the shoreline. We detected bluegill eDNA in all the ponds where bluegills were observed visually and some where bluegills were not observed. Bluegills were also less prevalent on the islands than the mainland, likely owing to limited dispersal and introduction by humans. Our eDNA method simply and rapidly detects the presence of this invasive fish species with less disturbance to the environment during field surveys than traditional methods.
Scientific Activity Is a Better Predictor of Nobel Award Chances than Dietary Habits and Economic Factors
Hideyuki Doi, Alexandre Heeren, Pierre Maurage
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0092612
Abstract: Several recent studies have described a strong correlation between nutritional or economic data and the number of Nobel awards obtained across a large range of countries. This sheds new light on the intriguing question of the key predictors of Nobel awards chances. However, all these studies have been focused on a single predictor and were only based on simple correlation and/or linear model analysis. The main aim of the present study was thus to clarify this debate by simultaneously exploring the influence of food consumption (cacao, milk, and wine), economic variables (gross domestic product) and scientific activity (number of publications and research expenditure) on Nobel awards. An innovative statistical analysis, hierarchical partitioning, has been used because it enables us to reduce collinearity problems by determining and comparing the independent contribution of each factor. Our results clearly indicate that a country's number of Nobel awards can be mainly predicted by its scientific achievements such as number of publications and research expenditure. Conversely, dietary habits and the global economy variable are only minor predictors; this finding contradicts the conclusions of previous studies. Dedicating a large proportion of the GDP to research and to the publication of a high number of scientific papers would thus create fertile ground for obtaining Nobel awards.
Interleukin-4 downregulates the cyclic tensile stress-induced matrix metalloproteinases-13 and cathepsin b expression by rat normal chondrocytes
Doi,Hideyuki,Nishida,Keiichiro,Yorimitsu,Masanori,Komiyama,Takamitsu
Acta Medica Okayama , 2008,
Abstract: Mechanical stress plays a key role in the pathogenesis of cartilage destruction seen in osteoarthritis (OA). We investigated the effect of cyclic tensile stress (CTS) on the anabolic and catabolic gene expression of rat cultured normal chondrocytes using the Flexercell strain unit. The effects of interleukin (IL)-4, a chondroprotective cytokine, on the changes in gene expression induced by CTS were also investigated. CTS (7% elongation at 0.5 Hz) for 24 h did not affect the expression of aggrecan and type II collagen, whereas CTS significantly upregulated matrix metalloproteinase (MMP)-13 and cathepsin B mRNA expression by chondrocytes. IL-1beta expression was also signifi cantly upregulated by CTS up to 12 h. The upregulation of MMP-13 was observed at 3 h, which was earlier than that of IL-1beta. Furthermore, pre-treatment with IL-4 (10 ng/ml) suppressed both MMP-13 and cathepsin B induction by mechanical stress, as well as CTS-induced IL-1beta expression. Our results suggest that IL-4 might have a therapeutic value in the treatment of OA by downregulation of mechanical stress-induced MMP-13 and cathepsin B expression by chondrocytes.
Decreased levels of insulin-like growth factor-1 and vascular endothelial growth factor relevant to the ossification disturbance in femoral heads spontaneous hypertensive rats.
Komiyama,Takamitsu,Nishida,Keiichiro,Yorimitsu,Masanori,Doi,Hideyuki
Acta Medica Okayama , 2006,
Abstract: Ossification disturbance in femoral head reportedly is seen in the Spontaneously Hypertensive rats (SHR) between ages of 10 and 20 weeks. We investigated serum and tissue levels of insulin-like growth factor-1 (IGF-1) and vascular endothelial growth factor (VEGF) in SHR relevant to the ossification disturbance and osteonecrosis of the femoral head. Serum levels of IGF-1 and VEGF were significantly lower in SHR than in Wistar Kyoto rats (WKY) at weeks 5, 10, 15 and 20 (p<0.005). The incidence of histological ossification disturbance of the femoral head was higher in SHR (59%) than in WKY (40%) at week 20. Lower serum and local levels of VEGF in SHR appeared to be related to the incomplete ossification of the femoral heads. Immunohistochemical study showed significantly lower numbers of IGF-1 and VEGF positive chondrocytes in the femoral epiphyseal cartilage of SHR than in those of WKY at weeks 10, 15 and 20. Our results suggest that local and/or systemic levels of IGF-1 and VEGF between ages of 5 and 20 weeks might play roles in the pathogenesis of ossifi cation disturbance of the femoral head in SHR.
Shorter Food Chain Length in Ancient Lakes: Evidence from a Global Synthesis
Hideyuki Doi, M. Jake Vander Zanden, Helmut Hillebrand
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0037856
Abstract: Food webs may be affected by evolutionary processes, and effective evolutionary time ultimately affects the probability of species evolving to fill the niche space. Thus, ecosystem history may set important evolutionary constraints on community composition and food web structure. Food chain length (FCL) has long been recognized as a fundamental ecosystem attribute. We examined historical effects on FCL in large lakes spanning >6 orders of magnitude in age. We found that food chains in the world’s ancient lakes (n = 8) were significantly shorter than in recently formed lakes (n = 10) and reservoirs (n = 3), despite the fact that ancient lakes harbored much higher species richness, including many endemic species. One potential factor leading to shorter FCL in ancient lakes is an increasing diversity of trophic omnivores and herbivores. Speciation could simply broaden the number of species within a trophic group, particularly at lower trophic levels and could also lead to a greater degree of trophic omnivory. Our results highlight a counter-intuitive and poorly-understood role of evolutionary history in shaping key food web properties such as FCL.
Estimation of Fish Biomass Using Environmental DNA
Teruhiko Takahara, Toshifumi Minamoto, Hiroki Yamanaka, Hideyuki Doi, Zen'ichiro Kawabata
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0035868
Abstract: Environmental DNA (eDNA) from aquatic vertebrates has recently been used to estimate the presence of a species. We hypothesized that fish release DNA into the water at a rate commensurate with their biomass. Thus, the concentration of eDNA of a target species may be used to estimate the species biomass. We developed an eDNA method to estimate the biomass of common carp (Cyprinus carpio L.) using laboratory and field experiments. In the aquarium, the concentration of eDNA changed initially, but reached an equilibrium after 6 days. Temperature had no effect on eDNA concentrations in aquaria. The concentration of eDNA was positively correlated with carp biomass in both aquaria and experimental ponds. We used this method to estimate the biomass and distribution of carp in a natural freshwater lagoon. We demonstrated that the distribution of carp eDNA concentration was explained by water temperature. Our results suggest that biomass data estimated from eDNA concentration reflects the potential distribution of common carp in the natural environment. Measuring eDNA concentration offers a non-invasive, simple, and rapid method for estimating biomass. This method could inform management plans for the conservation of ecosystems.
Feeding habits of omnivorous Asplanchna: comparison of diet composition among Asplanchna herricki, A. priodonta and A. girodi in pond ecosystems
Kwang-Hyeon CHANG,Hideyuki DOI,Yuichiro NISHIBE,Shin-ichi NAKANO
Journal of Limnology , 2010, DOI: 10.4081/jlimnol.2010.209
Abstract: Spatial distribution and the diet composition of Asplanchna species were studied in 18 water bodies in Matsuyama, Japan. The abundance of Asplanchna and other rotifers, crustaceans, phytoplankton and microbial plankton, together with basic environmental parameters, were determined between October and December 2006, and the distribution and diet composition of Asplanchna species were estimated. Three species of Asplanchna, A. herricki, A. priodonta and A. girodi were found in the present study, but A. herricki was rather less abundant than the other two species. Their diet composition was different among the species, showing that A. herricki consumed only particulate matter while the diet of A. priodonta included mainly phytoplankton, dominated by dinoflagellates. In contrast, A. girodi was rather carnivorous, and included other rotifers in its diet. Their different food habits are not explained by their morphotypes and trophi structures, suggesting this difference might be related to their feeding abilities. For A. girodi, prey selectivity (Chesson's α) for rotifer prey was negative, except for Keratella cochlearis. The amount of rotifers consumed was also low at a mean prey number of less than 3 per A. girodi gut. The result suggests that the predation impact of Asplanchna as a top-down controller of rotifer populations is species-specific and can be apparent only when Asplanchna population reaches high density in these ponds. From the present results, three Asplanchna species were found to belong to basically different feeding groups, A. herricki is detritivore while A. priodonta and A. girodi are omnivores; but A. girodi is more predacious.
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