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Search Results: 1 - 10 of 413 matches for " Ryohei Yamaoka "
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Cuticular Hydrocarbon Content that Affects Male Mate Preference of Drosophila melanogaster from West Africa
Aya Takahashi,Nao Fujiwara-Tsujii,Ryohei Yamaoka,Masanobu Itoh,Mamiko Ozaki,Toshiyuki Takano-Shimizu
International Journal of Evolutionary Biology , 2012, DOI: 10.1155/2012/278903
Abstract: Intraspecific variation in mating signals and preferences can be a potential source of incipient speciation. Variable crossability between Drosophila melanogaster and D. simulans among different strains suggested the abundance of such variations. A particular focus on one combination of D. melanogaster strains, TW1(G23) and Mel6(G59), that showed different crossabilities to D. simulans, revealed that the mating between females from the former and males from the latter occurs at low frequency. The cuticular hydrocarbon transfer experiment indicated that cuticular hydrocarbons of TW1 females have an inhibitory effect on courtship by Mel6 males. A candidate component, a C25 diene, was inferred from the gas chromatography analyses. The intensity of male refusal of TW1 females was variable among different strains of D. melanogaster, which suggested the presence of variation in sensitivity to different chemicals on the cuticle. Such variation could be a potential factor for the establishment of premating isolation under some conditions. 1. Introduction Drosophila exhibits complex mating behavior with frequent wing vibration and copulation attempts by males. The successful mating is achieved by communications between males and females using chemical, acoustic, and visual signals (reviewed in [1]). Subtle differences in these signals may accumulate during or after the formation of reproductive isolation. Once reproduction isolation is established to a certain extent, the correct mate recognition is essential to avoid costly hybridization and wasting time on unsuccessful courtship. Indeed, a certain degree of premating isolation or mating incompatibility is commonly observed between closely related species of Drosophila [2, 3]. In some cosmopolitan species of Drosophila, for example, D. ananassae [4] and D. elegans [5, 6], widely observed mating incompatibilities between populations from different locations exist. The degree of incompatibility is variable among sampled strains in these species. Another cosmopolitan species, D. melanogaster, also harbors incompatible combinations of populations [7–11]. The degree of incompatibility between populations is also variable, and many intermediate strains are typically observed. These within species incompatibilities suggest that there are many intraspecific variations in mating signals and preferences. Those variations could either fix in isolated populations or become targets of sexual selection under some conditions and consequently result in divergent mating-associated characters among different populations. It is
Ants Use Partner Specific Odors to Learn to Recognize a Mutualistic Partner
Masaru K. Hojo, Ari Yamamoto, Toshiharu Akino, Kazuki Tsuji, Ryohei Yamaoka
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0086054
Abstract: Regulation via interspecific communication is an important for the maintenance of many mutualisms. However, mechanisms underlying the evolution of partner communication are poorly understood for many mutualisms. Here we show, in an ant-lycaenid butterfly mutualism, that attendant ants selectively learn to recognize and interact cooperatively with a partner. Workers of the ant Pristomyrmex punctatus learn to associate cuticular hydrocarbons of mutualistic Narathura japonica caterpillars with food rewards and, as a result, are more likely to tend the caterpillars. However, the workers do not learn to associate the cuticular hydrocarbons of caterpillars of a non-ant-associated lycaenid, Lycaena phlaeas, with artificial food rewards. Chemical analysis revealed cuticular hydrocarbon profiles of the mutualistic caterpillars were complex compared with those of non-ant-associated caterpillars. Our results suggest that partner-recognition based on partner-specific chemical signals and cognitive abilities of workers are important mechanisms underlying the evolution and maintenance of mutualism with ants.
A Novel Role for Adipose Ephrin-B1 in Inflammatory Response
Takuya Mori, Norikazu Maeda, Kana Inoue, Ryohei Sekimoto, Yu Tsushima, Keisuke Matsuda, Masaya Yamaoka, Takayoshi Suganami, Hitoshi Nishizawa, Yoshihiro Ogawa, Tohru Funahashi, Iichiro Shimomura
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0076199
Abstract: Aims Ephrin-B1 (EfnB1) was selected among genes of unknown function in adipocytes or adipose tissue and subjected to thorough analysis to understand its role in the development of obesity. Methods and Results EfnB1 mRNA and protein levels were significantly decreased in adipose tissues of obese mice and such reduction was mainly observed in mature adipocytes. Exposure of 3T3-L1 adipocytes to tumor necrosis factor-α (TNF-α) and their culture with RAW264.7 cells reduced EFNB1 levels. Knockdown of adipose EFNB1 increased monocyte chemoattractant protein-1 (Mcp-1) mRNA level and augmented the TNF-α-mediated THP-1 monocyte adhesion to adipocytes. Adenovirus-mediated adipose EFNB1-overexpression significantly reduced the increase in Mcp-1 mRNA level induced by coculture of 3T3-L1 adipocytes with RAW264.7 cells. Monocyte adherent assay showed that adipose EfnB1-overexpression significantly decreased the increase of monocyte adhesion by coculture with RAW264.7 cells. TNF-α-induced activation of extracellular signal-regulated kinase 1/2 (ERK1/2) was reduced by EFNB1-overexpression. Conclusions EFNB1 contributes to the suppression of adipose inflammatory response. In obesity, reduction of adipose EFNB1 may accelerate the vicious cycle involved in adipose tissue inflammation.
Possible Involvement of Opa-Interacting Protein 5 in Adipose Proliferation and Obesity
Kana Inoue, Norikazu Maeda, Takuya Mori, Ryohei Sekimoto, Yu Tsushima, Keisuke Matsuda, Masaya Yamaoka, Takayoshi Suganami, Hitoshi Nishizawa, Yoshihiro Ogawa, Tohru Funahashi, Iichiro Shimomura
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0087661
Abstract: Obesity is an epidemic matter increasing risk for cardiovascular diseases and metabolic disorders such as type 2 diabetes. We recently examined the association between visceral fat adiposity and gene expression profile of peripheral blood cells in human subjects. In a series of studies, Opa (Neisseria gonorrhoeae opacity-associated)-interacting protein 5 (OIP5) was nominated as a molecule of unknown function in adipocytes and thus the present study was performed to investigate the role of OIP5 in obesity. Adenovirus overexpressing Oip5 (Ad-Oip5) was generated and infected to 3T3-L1 cells stably expressing Coxsackie-Adenovirus Receptor (CAR-3T3-L1) and to mouse subcutaneous fat. For a knockdown experiment, siRNA against Oip5 (Oip5-siRNA) was introduced into 3T3-L1 cells. Proliferation of adipose cells was measured by BrdU uptake, EdU-staining, and cell count. Significant increase of Oip5 mRNA level was observed in obese white adipose tissues and such increase was detected in both mature adipocytes fraction and stromal vascular cell fraction. Ad-Oip5-infected CAR-3T3-L1 preadipocytes and adipocytes proliferated rapidly, while a significant reduction of proliferation was observed in Oip5-siRNA-introduced 3T3-L1 preadipocytes. Fat weight and number of adipocytes were significantly increased in Ad-Oip5-administered fat tissues. Oip5 promotes proliferation of pre- and mature-adipocytes and contributes adipose hyperplasia. Increase of Oip5 may associate with development of obesity.
Extension of Chronological Life in Saccharomyces cerevisiae under Ethanol Stress by Thermally Processed Rice Koji Extracts  [PDF]
Chizuru Yamaoka, Osamu Kurita
Advances in Microbiology (AiM) , 2016, DOI: 10.4236/aim.2016.69058
Abstract: The effect of thermally processed rice koji extracts on survival of yeast Saccharomyces cerevisiae was examined in comparison with non-heated koji extract. In chronological life span (CLS) tests on high-sugar fermentation, the survivals of the yeast cells grown with heated koji extracts were higher than non-heated koji extract. Heat treatment of the extracts by autoclaving led to a loss in most of amino acids due to the Maillard reaction, although histidine contents slightly increased. In glucose-arginine mixtures, arginine was partly converted to histidine by autoclaving and the addition of histidine prolonged the CLS of yeast cells. The yeast cells grown with the non-heated extracts were more resistant to oxidative stress whereas the antioxidant activities were lower than those of the heated extracts. The yeast cells grown with the heated extracts were more tolerant to ethanol and had a higher reduction capacity in the late stationary phase when the cells were incubated in the presence of ethanol. Maillard reaction products elevated the levels of reactive oxygen species to yeast cells grown under ethanol stress in the late stationary phase. These results suggest that thermally processed koji extracts can act as a protectant against ethanol stress during the late stationary phase of yeast growth and extend the CLS due to the increase of histidine contents by autoclaving.
Error Correction of Enumerative Induction of Deterministic Context-free L-system Grammar
Ryohei Nakano
IAENG International Journal of Computer Science , 2013,
Abstract:
Khovanov homology and Rasmussen's s-invariants for pretzel knots
Ryohei Suzuki
Mathematics , 2006,
Abstract: We calculated the rational Khovanov homology of some class of pretzel knots, by using the spectral sequence constructed by P. Turner. Moreover, we determined the Rasmussen's s-invariant of almost of pretzel knots with three pretzels.
Infinite Sparse Block Model with Text Using 2DCRP
Ryohei Hisano
Statistics , 2015,
Abstract: A fundamental step in understanding the topology of a network is to uncover its latent block structure. To estimate the latent block structure with more accuracy, I propose an extension of the sparse block model, incorporating node textual information and an unbounded number of roles and interactions. The latter task is accomplished by extending the well-known Chinese restaurant process to two dimensions. Inference is based on collapsed Gibbs sampling, and the model is evaluated on both synthetic and real-world interfirm buyer-seller network datasets.
Pathogenesis of Helicobacter pylori-Related Gastroduodenal Diseases from Molecular Epidemiological Studies
Yoshio Yamaoka
Gastroenterology Research and Practice , 2012, DOI: 10.1155/2012/371503
Abstract: Helicobacter pylori is a major human pathogen that infects the stomach and produces inflammation that is responsible for various gastroduodenal diseases. Despite the high prevalence of H. pylori infections in Africa and South Asia, the incidence of gastric cancer in these areas is much lower than in other countries. The incidence of gastric cancer also tends to decrease from north to south in East Asia. Data from molecular epidemiological studies show that this variation in different geographic areas could be explained in part by different types of H. pylori virulence factors, especially CagA, VacA, and OipA. H. pylori infection is thought to be involved in both gastric cancer and duodenal ulcer, which are at opposite ends of the disease spectrum. This discrepancy can also be explained in part by another H. pylori factor, DupA, as well as by CagA typing (East Asian type versus Western type). H. pylori has a genome of approximately 1,600 genes; therefore, there might be other novel virulence factors. Because genome wide analyses using whole-genome sequencing technology give a broad view of the genome of H. pylori, we hope that next-generation sequencers will enable us to efficiently investigate novel virulence factors. 1. Introduction Helicobacter pylori is a gram-negative spiral bacterium whose ecological niche is the human stomach. It is a major human pathogen that infects the stomach and produces inflammation that is responsible for diseases, such as duodenal ulcer, gastric ulcer, gastric cancer, and mucosa-associated lymphoid tissue lymphoma. Despite a general decline in the incidence of gastric cancer, it remains the fourth most common cancer and second leading cause of cancer-related deaths worldwide (http://globocan.iarc.fr/). Interestingly, despite the high prevalence of H. pylori infections in Africa and South Asia, the incidence of gastric cancer in these areas is much lower than in other countries; these phenomena are called African enigmas and Asian enigmas [1] (Table 1). Furthermore, the incidence of gastric cancer has a tendency to decrease from north to south in East Asia. The pathogenesis of the different clinical outcomes is multifactorial with environmental factors (mainly diet) often playing a dominant role and with an influence by host factors, especially those governing the severity of the immune response as well as the virulence of the infecting organism. Table 1: Incidence of gastric cancer in 2008. H. pylori, which is highly heterogeneous, has a genome of approximately 1,600 genes, the majority of which have been functionally
Roles of Helicobacter pylori BabA in gastroduodenal pathogenesis
Yoshio Yamaoka
World Journal of Gastroenterology , 2008,
Abstract: Interactions between BabA and Lewis b (Leb) related antigens are the best characterized adhesin-receptor interactions in Helicobacter pylori (H pylori). Several mechanisms for the regulation of BabA expression are predicted, including at both transcriptional and translational levels. The formation of chimeric proteins (babA/B or babB/A chimeras) seems to play an especially important role in translational regulation. Chimeric BabB/A protein had the potential to bind Leb; however, protein production was subject to phase variation through slipped strand mispairing. The babA gene was cloned initially from strain CCUG17875, which contains a silent babA1 gene and an expressed babA2 gene. The sequence of these two genes differs only by the presence of a 10 bp deletion in the signal peptide sequence of babA1 that eliminates its translational initiation codon. However, the babA1 type deletion was found only in strain CCUG17875. A few studies evaluated BabA status by immunoblot and confirmed that BabA-positive status in Western strains was closely associated with severe clinical outcomes. BabA-positive status also was associated with the presence of other virulence factors (e.g. cagA-positive status and vacA s1 genotype). A small class of strains produced low levels of the BabA protein and lacked Leb binding activity. These were more likely to be associated with increased mucosal inflammation and severe clinical outcomes than BabA-positive strains that exhibited Leb binding activity. The underlying mechanism is unclear, and further studies will be necessary to investigate how the complex BabA-receptor network is functionally coordinated during the interaction of H pylori with the gastric mucosa.
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