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91.
Quantitative food webs were constructed to explore the community structure of leaf-mining moths in the family Gracillariidae
and their parasitoid wasps in a deciduous forest in Hokkaido, Japan. A whole food web was constructed from data collected
from June to October 2001. In the web, 16 leafminer species on seven tree species were attacked by 58 species of hymenopteran
parasitoid; 376 links between leafminers and parasitoids were observed. Leafminers were specialist herbivores, but most parasitoids
were generalists. Five webs were constructed for the seasonal prevalence of leafminers over the one-year period to reveal
the temporal dynamics in community structure. Among the seasonal webs, the first web in June was distinctive because two tree
species, Japanese umbrella tree Magnolia obovata and Japanese magnolia M. kobus, supported the community. Second to fourth webs from July to September were dominated by the leafminer species on Japanese
oak Quercus
crispula, and the fifth web was marked by that on Carpinus
cordata. The extent of potential apparent competition among leafminers was evaluated using quantitative parasitoid overlap diagrams.
These diagrams suggested that abundant host species are likely to have large indirect effects on less abundant species. Moreover,
the potential for apparent competition between leafminer species inhabiting different host tree species can occur, although
leafminers sharing the same tree species are prone to interact via shared parasitoids. In this system, particular leafminer
species, acting as potential sources of apparent competition, can affect other species as sinks, and control whole-community
dynamics. Directed apparent competition may potentially occur around oak trees. 相似文献
92.
The specialization of herbivores among tree species is poorly understood despite its fundamental importance as a factor regulating
diversity. To examine the effect of tree species on larval community structure, the larval communities in 10 temperate deciduous
tree species that differed in leaf emergence pattern (flush- vs. intermediate-type) were seasonally surveyed. The newly developed
soft, nitrogen-rich leaves of all species became tough and nitrogen-poor as the season progressed. Following the changes in
leaf quality, two distinct seasonal lepidopteran larval communities emerged, with a marked turnover in early July. The beta
diversity, or dissimilarity, of species composition in the larval communities among tree species was higher in summer than
in spring. These results imply that the lepidopteran larval communities as a whole were supported by alpha diversity in spring
and by beta diversity in summer, demonstrating that the plant diversity of this forest could support a caterpillar community.
We examined the importance of spatio-temporal variations in leaf quality within and among tree species in promoting herbivore
diversity, although other factors, such as tree species phylogeny and predators, may also have a large effect on lepidopteran
larval communities. 相似文献
93.
Doihara Hitoshi Nozawa Katsura Kojima Ryosuke Kawabata-Shoda Eri Yokoyama Toshihide Ito Hiroyuki 《Molecular and cellular biochemistry》2009,331(1-2):239-245
Molecular and Cellular Biochemistry - Recently, we discovered that transient receptor potential ankyrin1 channel (TRPA1) is highly expressed in human and rat enterochromaffin (EC) cells, and those... 相似文献
94.
Akimitsu Miyaji Masashi Suzuki Toshihide Baba Toshiaki Kamachi Ichiro Okura 《Journal of Molecular Catalysis .B, Enzymatic》2009,57(1-4):211-215
Particulate methane monooxygenase (pMMO), a copper-containing membrane protein, catalyzes methane hydroxylation under aerobic conditions. We found that the activity of pMMO was increased by catalase, implying that hydrogen peroxide (H2O2) is generated by pMMO with duroquinol, an electron donor for pMMO, and that the generated H2O2 inhibits pMMO activity. In addition, reversible inhibition of pMMO with H2O2 was observed upon treatment of pMMO with H2O2 followed by the addition of catalase, and H2O2 formation by pMMO with duroquinol was detected using a fluorescence probe. The redox behavior of type 2 copper in pMMO measured by the electron paramagnetic resonance revealed that H2O2 re-oxidizes the type 2 copper in pMMO reduced with duroquinol. 相似文献
95.
Makoto Daimon Toshihide Oizumi Shigeru Karasawa Kiriko Wada Shinji Susa Isao Kubota Takeo Kato 《Biochemical and biophysical research communications》2009,386(1):26-29
The association of the Ser326Cys polymorphism of the 8-oxoguanine glycosylase 1 (OGG1) gene with type 2 diabetes was examined using a Japanese population (n (M/W): 4585 (2085/2500); age: 62.6 ± 10.9 years). HbA1c levels and frequency of diabetic subjects were significantly higher in subjects with genotypes with Cys allele than in those without (p = 0.032 and 0.037, respectively). Multiple logistic regression analysis showed that genotypes with Cys allele were significantly associated with diabetes (OR: 1.32, p = 0.0289). In subjects whose glucose tolerance was classified by FPG and 2-h PG (n = 1.634), the association was more substantial (genotypes with Cys allele vs. without, OR: 1.70, p = 0.0059; genotypes Cys/Cys vs. Ser/Ser, OR: 2.19, p = 0.0008). In subjects with genotype Ser/Ser, the insulin secretion index, HOMA-β, increased in the subjects with glucose intolerance and decreased in the subjects with diabetes, while, in subjects with genotypes Ser/Cys + Cys/Cys, HOMA-β decreased as the glucose tolerance progressed (p for trend = 0.010). 相似文献
96.
Xiaoxiang Liu Motonori Hashimoto Atsushi Yamaguchi Toshihide Yamashita 《Biochemical and biophysical research communications》2009,382(4):795-18400
Neuronal axons are guided by attractive and repulsive cues in their local environment. Since the identification of the repulsive guidance molecule (RGM) a (RGMa) as an axon repellent in the visual system, diverse functions, as part of the developing and adult central nervous system (CNS), have been ascribed to it. The binding of RGMa to its receptor neogenin has been shown to induce RhoA activation, leading to inhibitory/repulsive behavior and the collapse of the neuronal growth cone. In this paper, we provide evidence to suggest the involvement of RGMb, another member of the RGM family, in the rat CNS. RGMb inhibits neurite outgrowth in postnatal cerebellar granule neurons (CGNs) in vitro. RGMb is expressed by oligodendrocytes and neurons in the adult rat CNS, and the expression of this molecule is upregulated around the site of spinal cord injury. RGMb is present in myelin isolated from an adult rat brain. RGMb and neogenin are coexpressed in CGNs and entorhinal cortex neurons. These findings suggest that RGMb is a myelin-derived inhibitor of axon growth in the CNS. Inhibition of RGMb may provide an alternative approach for the treatment of spinal injuries. 相似文献
97.
Katsuhiko Hata Kozo Kaibuchi Shinobu Inagaki Toshihide Yamashita 《The Journal of cell biology》2009,184(5):737-750
Neuronal axons are guided by attractive and repulsive cues in their local environment. Because the repulsive guidance molecule A (RGMa) was originally identified as an axon repellent in the visual system, diverse functions in the developing and adult central nervous system have been ascribed to it. RGMa binding to its receptor neogenin induces RhoA activation, leading to inhibitory/repulsive behavior and collapse of the neuronal growth cone. However, the precise mechanisms that regulate RhoA activation are poorly understood. In this study, we show that Unc5B, a member of the netrin receptor family, interacts with neogenin as a coreceptor for RGMa. Moreover, leukemia-associated guanine nucleotide exchange factor (LARG) associates with Unc5B to transduce the RhoA signal. Focal adhesion kinase (FAK) is involved in RGMa-induced tyrosine phosphorylation of LARG as well as RhoA activation. These findings uncover the molecular basis for diverse functions mediated by RGMa. 相似文献
98.
Yukiko Kaneko Toshihide Kimura Midori Souma Yuka Kimura Ichiro Niki 《FEBS letters》2009,583(2):377-38
We examined the expression of the major H2S-producing enzymes, cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE). CBS was ubiquitously distributed in the mouse pancreas, but CSE was found only in the exocrine. Freshly isolated islets expressed CBS, while CSE was faint. However, high glucose increased the CSE expression in the beta-cells. l-Cysteine or NaHS suppressed islet cell apoptosis with high glucose, and increased glutathione content in MIN6 beta-cells. Pretreatment with l-cysteine improved the secretory responsiveness following stimulation with glucose. The CSE inhibitor dl-propargylglycine antagonized these l-cysteine effects. We suggest H2 S may function as an ‘intrinsic brake’ which protects beta-cells from glucotoxicity. 相似文献
99.
Raman Deep Singh David L. Marks Eileen L. Holicky Christine L. Wheatley Tatiana Kaptzan Satoshi B. Sato Toshihide Kobayashi Kun Ling Richard E. Pagano 《Traffic (Copenhagen, Denmark)》2010,11(3):348-360
Caveolae are plasma membrane domains involved in the uptake of certain pathogens and toxins. Internalization of some cell surface integrins occurs via caveolae suggesting caveolae may play a crucial role in modulating integrin‐mediated adhesion and cell migration. Here we demonstrate a critical role for gangliosides (sialo‐glycosphingolipids) in regulating caveolar endocytosis in human skin fibroblasts. Pretreatment of cells with endoglycoceramidase (cleaves glycosphingolipids) or sialidase (modifies cell surface gangliosides and glycoproteins) selectively inhibited caveolar endocytosis by >70%, inhibited the formation of plasma membrane domains enriched in sphingolipids and cholesterol (‘lipid rafts'), reduced caveolae and caveolin‐1 at the plasma membrane by approximately 80%, and blunted activation of β1‐integrin, a protein required for caveolar endocytosis in these cells. These effects could be reversed by a brief incubation with gangliosides (but not with asialo‐gangliosides or other sphingolipids) at 10°C, suggesting that sialo‐lipids are critical in supporting caveolar endocytosis. Endoglycoceramidase treatment also caused a redistribution of focal adhesion kinase, paxillin, talin, and PIP Kinase Iγ away from focal adhesions. The effects of sialidase or endoglycoceramidase on membrane domains and the distribution of caveolin‐1 could be recapitulated by β1‐integrin knockdown. These results suggest that both gangliosides and β1‐integrin are required for maintenance of caveolae and plasma membrane domains. 相似文献
100.
Myelin-associated glycoprotein inhibits microtubule assembly by a Rho-kinase-dependent mechanism 总被引:2,自引:0,他引:2
Mimura F Yamagishi S Arimura N Fujitani M Kubo T Kaibuchi K Yamashita T 《The Journal of biological chemistry》2006,281(23):15970-15979
Myelin-associated glycoprotein (MAG) and Nogo are potent inhibitors of neurite outgrowth from a variety of neurons, and they have been identified as possible components of the central nervous system myelin that prevents axonal regeneration in the adult vertebrate central nervous system. The activation of RhoA and Rho-kinase is reported to be an essential part of the signaling mechanism of these proteins. Here, we report that the collapsing response mediator protein-2 (CRMP-2) is phosphorylated by a Rho-kinase-dependent mechanism downstream of MAG or Nogo-66. The overexpression of the nonphosphorylated form of CRMP-2 at threonine 555, which is the phosphorylation site for Rho-kinase, counteracts the inhibitory effect of MAG on the postnatal cerebellar neurons. Additionally, the expression of the dominant negative form of CRMP-2 or knockdown of the gene using small interference RNA (siRNA) mimics the effect of MAG in vitro. Consistent with the function of CRMP-2, which promotes microtubule assembly, microtubule levels are down-regulated in the cerebellar neurons that are stimulated with MAG in vitro. Reduction in the density of microtubules is also observed in the injured axons following the spinal cord injury, and this effect depends on the Rho-kinase activity. Our data suggest the important roles of CRMP-2 and microtubules in the inhibition of the axon regeneration by the myelin-derived inhibitors. 相似文献