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11.
Lucas P. Medeiros Stefano Allesina Vasilis Dakos George Sugihara Serguei Saavedra 《Ecology letters》2023,26(1):170-183
Managing ecological communities requires fast detection of species that are sensitive to perturbations. Yet, the focus on recovery to equilibrium has prevented us from assessing species responses to perturbations when abundances fluctuate over time. Here, we introduce two data-driven approaches (expected sensitivity and eigenvector rankings) based on the time-varying Jacobian matrix to rank species over time according to their sensitivity to perturbations on abundances. Using several population dynamics models, we demonstrate that we can infer these rankings from time-series data to predict the order of species sensitivities. We find that the most sensitive species are not always the ones with the most rapidly changing or lowest abundance, which are typical criteria used to monitor populations. Finally, using two empirical time series, we show that sensitive species tend to be harder to forecast. Our results suggest that incorporating information on species interactions can improve how we manage communities out of equilibrium. 相似文献
12.
Yukio Imanishi Masao Tanihara Toshiharu Sugihara Toshinobu Higashimura 《Biopolymers》1977,16(10):2203-2215
A histidine-containing cyclic dipeptide, cyclo(D -Leu-L -His), was almost 20 times as efficient a catalyst as imidazole in the hydrolysis of p-nitrophenyl laurate. The effect of dioxane on the hydrolysis showed that hydrophobic interaction between the cyclic dipeptide and the ester is very important. This reaction obeyed the Michaelis-Menten kinetics, and the Michaelis constant Km was as low as 9.98 × 10?5M. Since the linear dipeptide having D -Leu-L -His sequence was nearly inactive in the hydrolysis, the functional groups of cyclo(D -Leu-L -His) in a specific arrangement held by the rigid backbone must have cooperated in the fast hydrolysis. Very weak catalysis by the diasteremeric cyclic dipeptide, cyclo(L -Leu-L -His), in the hydrolysis supported the above view. 相似文献
13.
Drosophila choline acetyltransferase uses a non-AUG initiation codon and full length RNA is inefficiently translated 总被引:11,自引:0,他引:11
RNA from a partial cDNA clone containing the entire protein coding sequence of Drosophila melanogaster acetyl-CoA:choline O-acetyltransferase (EC 2.3.1.6; choline acetyltransferase) can be translated into active enzyme. This is unusual since this partial cDNA clone contains no appropriate ATG (AUG) initiation codon. In this study we use in vitro deletion and point mutants to identify GTG as the starting codon for protein translation. We also report the sequence of a full length Drosophila choline acetyltransferase cDNA and demonstrate that RNA produced by this clone is translated into active choline acetyltransferase but at a significantly reduced efficiency when compared to the partial cDNA clone. These results indicate that translational control may be an important regulatory step in production of Drosophila choline acetyltransferase. 相似文献
14.
Mitsumasa Haruna Makiko Kato Kazuo Ito Toshiaki Nikai Hisayoshi Sugihara Hiroyuki Muratat 《Phytochemistry》1981,20(11):2583-2584
Angeloylcumambrin-B, a new antimicrobial guaianolide sesquiterpene lactone, was isolated from Chrysanthemum ornatum and the structure was determined by a combination of chemical and physical methods. 相似文献
15.
Hana Shimoyama Toshiaki K. Shibata Masahiko Ito Tomoaki Oda Toshiya Itoh Mari Mukai Madoka Matsuya-Ogawa Masashi Adachi Hirotake Murakami Takeshi Nakayama Kazuhiro Sugihara Hiroaki Itoh Tetsuro Suzuki Naohiro Kanayama 《Biochemistry and Biophysics Reports》2020
Endometrial cancer is the most common gynecologic malignancy and is associated with increased morbidity each year, including young people. However, its mechanisms of proliferation and progression are not fully elucidated. It is well known that abnormal glycosylation is involved in oncogenesis, and fucosylation is one of the most important types of glycosylation. In particular, fucosyltransferase 8 (FUT8) is the only FUT responsible for α1, 6-linked fucosylation (core fucosylation), and it is involved in various physiological as well as pathophysiological processes, including cancer biology. Therefore, we aimed to identify the expression of FUT8 in endometrial endometrioid carcinoma and investigate the effect of the partial silencing of the FUT8 gene on the cell proliferation of Ishikawa cells, an epithelial-like endometrial cancer cell line. Quantitative real-time PCR analysis showed that FUT8 gene expression was significantly elevated in the endometrial endometrioid carcinoma, compared to the normal endometrium. The immunostaining of FUT8 and Ulex europaeus Agglutinin 1 (UEA-1), a kind of lectin family specifically binding to fucose, was detected endometrial endometrioid carcinoma. The proliferation assay showed FUT8 partial knockdown by transfection of siRNA significantly suppressed the proliferation of Ishikawa cells, concomitant with the upregulation in the gene expressions associated with the interesting pathways associated with de-ubiquitination, aspirin trigger, mesenchymal-epithelial transition (MET) et al. It was suggested that the core fucosylation brought about by FUT8 might be involved in the proliferation of endometrial endometrioid carcinoma cells. 相似文献
16.
Hidetaka Sugihara Takatsugu Ishimoto Masayuki Watanabe Hiroshi Sawayama Masaaki Iwatsuki Yoshifumi Baba Yoshihiro Komohara Motohiro Takeya Hideo Baba 《PloS one》2013,8(11)
Bmi1 is overexpressed in a variety of human cancers including gastrointestinal cancer. The high expression level of Bmi1 protein is associated with poor prognosis of gastrointestinal cancer patients. On the other hand, tumor-associated macrophages (TAMs) contribute to tumor growth, invasion, and metastasis by producing various mediators in the tumor microenvironment. The aim of this study was to investigate TAM-mediated regulation of Bmi1 expression in gastrointestinal cancer. The relationship between TAMs and Bmi1 expression was analyzed by immunohistochemistry and quantitative real-time PCR (qRT-PCR), and results showed a positive correlation with tumor-infiltrating macrophages (CD68 and CD163) and Bmi1 expression in cancer cells. Co-culture with TAMs triggered Bmi1 expression in cancer cell lines and enhanced sphere formation ability. miRNA microarray analysis of a gastric cancer cell line co-cultured with macrophages was conducted, and using in silico methods to analyze the results, we identified miR-30e* as a potential regulator of Bmi1 expression. Luciferase assays using miR-30e* mimic revealed that Bmi1 was a direct target for miR-30e* by interactions with the putative miR-30e* binding sites in the Bmi1 3′ untranslated region. qRT-PCR analysis of resected cancer specimens showed that miR-30e* expression was downregulated in tumor regions compared with non-tumor regions, and Bmi1 expression was inversely correlated with miR-30e* expression in gastric cancer tissues, but not in colon cancer tissues. Our findings suggest that TAMs may cause increased Bmi1 expression through miR-30e* suppression, leading to tumor progression. The suppression of Bmi1 expression mediated by TAMs may thus represent a possible strategy as the treatment of gastrointestinal cancer. 相似文献
17.
Satomi Nadanaka Shaobo Zhou Shoji Kagiyama Naoko Shoji Kazuyuki Sugahara Kazushi Sugihara Masahide Asano Hiroshi Kitagawa 《The Journal of biological chemistry》2013,288(13):9321-9333
Mutant alleles of EXT1 or EXT2, two members of the EXT gene family, are causative agents in hereditary multiple exostoses, and their gene products function together as a polymerase in the biosynthesis of heparan sulfate. EXTL2, one of three EXT-like genes in the human genome that are homologous to EXT1 and EXT2, encodes a transferase that adds not only GlcNAc but also N-acetylgalactosamine to the glycosaminoglycan (GAG)-protein linkage region via an α1,4-linkage. However, both the role of EXTL2 in the biosynthesis of GAGs and the biological significance of EXTL2 remain unclear. Here we show that EXTL2 transfers a GlcNAc residue to the tetrasaccharide linkage region that is phosphorylated by a xylose kinase 1 (FAM20B) and thereby terminates chain elongation. We isolated an oligosaccharide from the mouse liver, which was not detected in EXTL2 knock-out mice. Based on structural analysis by a combination of glycosidase digestion and 500-MHz 1H NMR spectroscopy, the oligosaccharide was found to be GlcNAcα1-4GlcUAβ1–3Galβ1–3Galβ1–4Xyl(2-O-phosphate), which was considered to be a biosynthetic intermediate of an immature GAG chain. Indeed, EXTL2 specifically transferred a GlcNAc residue to a phosphorylated linkage tetrasaccharide, GlcUAβ1–3Galβ1–3Galβ1–4Xyl(2-O-phosphate). Remarkably, the phosphorylated linkage pentasaccharide generated by EXTL2 was not used as an acceptor for heparan sulfate or chondroitin sulfate polymerases. Moreover, production of GAGs was significantly higher in EXTL2 knock-out mice than in wild-type mice. These results indicate that EXTL2 functions to suppress GAG biosynthesis that is enhanced by a xylose kinase and that the EXTL2-dependent mechanism that regulates GAG biosynthesis might be a “quality control system” for proteoglycans. 相似文献
18.
Haruo Misono Kouji Sugihara Yumiko Kuwamoto Shinji Nagata Susumu Nagasaki 《Bioscience, biotechnology, and biochemistry》2013,77(6):1491-1498
Leucine dehydrogenase [EC 1.4.1.9] was purified to homogeneity from Corynebacterium pseudodiphtheriticum ICR 2210. The enzyme consisted of a single polypeptide with a molecular weight of about 34,000. Stepwise Edman degradation provided the N-terminal sequence of the first 24 amino acids, and carboxypeptidase Y digestion provided the C-terminal sequence of the last 2 amino acids. Although the enzyme catalyzed the reversible deamination of various branched-chain l-amino acids, l-valine was the best substrate for oxidative deamination at pH 10.9 and the saturated concentration. The enzyme, however, had higher reactivity for l-leucine, and the kcat/Km value for l-leucine was higher than that for l-valine. The enzyme required NAD+ as a natural coenzyme. The NAD+ analogs 3-acetylpyridine-NAD+ and deamino-NAD+ were much better coenzymes than NAD +. The enzyme activity was significantly reduced by sulfhydryl reagents and pyridoxal 5′-phosphate. d-Enantiomers of the substrate amino acids competitively inhibited the oxidation of l-valine. 相似文献
19.
Yamazaki Y Hozumi Y Kaneko K Sugihara T Fujii S Goto K Kato H 《Neuron glia biology》2007,3(4):325-334
Like neurons and astrocytes, oligodendrocytes have a variety of neurotransmitter receptors and ion channels. However, except for facilitating the rapid conduction of action potentials by forming myelin and buffering extracellular K(+), little is known about the direct involvement of oligodendrocytes in neuronal activities. To investigate their physiological roles, we focused on oligodendrocytes in the alveus of the rat hippocampal CA1 region. These cells were found to respond to exogenously applied glutamate by depolarization through N-methyl-D-aspartate (NMDA) receptors and non-NMDA receptors. Electrical stimulation of the border between the alveus and stratum oriens evoked inward currents through several routes involving glutamate receptors and inward rectifier K(+) channels. Moreover, electrical stimulation resembling in vivo activity evoked long-lasting depolarization. To examine the modulatory effects of oligodendrocytes on neuronal activities, we performed dual, whole-cell recording on CA1 pyramidal neurons and oligodendrocytes. Direct depolarization of oligodendrocytes shortened the latencies of action potentials evoked by antidromic stimulation. These results indicate that oligodendrocytes increase the conduction velocity of action potentials by a mechanism additional to saltatory conduction, and that they have active roles in information processing in the brain. 相似文献
20.
1. A hemorrhagic factor was isolated from Vipera a. aspis venom by gel filtration, ion-exchange chromatography and affinity chromatography. 2. Molecular weight of the purified factor was determined to be 67,000 Da, which was composed of 552 amino acid residues. 3. The minimum hemorrhagic dose (MHD) was measured to be 0.11 micrograms per mouse with subcutaneous injection. The hemorrhagic activity was inhibited by chelating agents and reductant. 4. The hemorrhagic factor possesses proteolytic activity against dimethylcasein. 5. Serum creatine phosphokinase level was rapidly increased within 30 min following injections of this preparation into the mice thighs. 6. Actin, one of the main components of muscle fiber, is apparently digested by the hemorrhagic factor. The pathological findings are further reported in this paper. 相似文献