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991.
Central-place foraging seabirds increase food-loads and decrease meal frequency when they forage in areas that are distant
from the breeding colony. In 2001–2002, we studied the seasonal changes in at-sea distribution, food-load mass, meal frequency,
and fledging mass in rhinoceros auklets (Cerorhinca monocerata), which forage in coastal waters during the day and feed their chicks at night. In both years, greater numbers of auklets
were observed flying in northern waters that are more distant from the colony in June (65 km) and July (65–66 km) than in
May (38–47 km). In July of both years, many auklets flew northward across the transect set 65–120 km north of the colony at
sunrise; the birds returned south again at sunset, indicating that they foraged in waters outside the study area. This seasonal
northward movement of the foraging area may reflect the migration of their main prey item, the Japanese anchovy (Engraulis japonicus), which move with the Tsushima Warm Current flowing from the southern Sea of Japan. Food-load mass did not increase seasonally.
In both years, the estimated daily meal frequency was lower in July than in May or June, partly because of the increased foraging
distance in July. Late-hatched chicks also displayed lighter fledging masses than early chicks in both years. We suggest that
late breeders are required to forage at great distances for longer periods, which may result in decreased meal frequency and
lighter fledging mass of their chicks. 相似文献
992.
We used terrestrial ecosystem models to estimate spatial and temporal variability in and uncertainty of estimated soil carbon
dioxide (CO2) efflux, or soil respiration, over the Japanese Archipelago. We compared five carbon-cycle models to assess inter-model variability:
Biome-BGC, CASA, LPJ, SEIB, and VISIT. These models differ in approaches to soil carbon dynamics, root respiration estimation,
and relationships between decomposition and environmental factors. We simulated the carbon budget of natural ecosystems over
the archipelago for 2001–2006 at 1-day time steps and 2-min (latitude and longitude) spatial resolution. The models were calibrated
using measured flux data to accurately represent net ecosystem CO2 exchange. Each model successfully reproduced seasonal changes and latitudinal gradients in soil respiration. The five-model
average of estimated total soil respiration of Japanese ecosystems was 295 Tg C year−1, with individual model estimates ranging from 210 to 396 Tg C year−1 (1 Tg = 1012 g). The differences between modeled estimates were more evident in summer and in warmer years, implying that they were mainly
attributable to differences in modeling the temperature dependence of soil respiration. There was a large discrepancy between
models in the estimated contribution of roots to total soil respiration, ranging from 3.9 to 48.4%. Although model calibration
reduced the uncertainty of flux estimates, substantial uncertainties still remained in estimates of underground processes
from these terrestrial carbon-cycle models. 相似文献
993.
Paula I. Moreira Xiongwei Zhu Xinglong Wang Hyoung-gon Lee Akihiko Nunomura Robert B. Petersen George Perry Mark A. Smith 《生物化学与生物物理学报:疾病的分子基础》2010,1802(1):212-220
Mitochondrial dysfunction has long been associated with neurodegenerative disease. Therefore, mitochondrial protective agents represent a unique direction for the development of drug candidates that can modify the pathogenesis of neurodegeneration. This review discusses evidence showing that mitochondrial dysfunction has a central role in the pathogenesis of Alzheimer's, Parkinson's and Huntington's diseases and amyotrophic lateral sclerosis. We also debate the potential therapeutic efficacy of metabolic antioxidants, mitochondria-directed antioxidants and Szeto–Schiller (SS) peptides. Since these compounds preferentially target mitochondria, a major source of oxidative damage, they are promising therapeutic candidates for neurodegenerative diseases. Furthermore, we will briefly discuss the novel action of the antihistamine drug Dimebon on mitochondria. 相似文献
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996.
Akihiko Mougi 《Ecology and evolution》2020,10(17):9192-9199
Ecosystems comprise living organisms and organic matter or detritus. In earlier community ecology theories, ecosystem dynamics were normally understood in terms of aboveground, green‐world trophic interaction networks, or food webs. Recently, there has been growing interest in the role played in ecosystem dynamics by detritus in underground, brown‐world interactions. However, the role of decomposers in the consumption of detritus to produce nutrients in ecosystem dynamics remains unclear. Here, an ecosystem model of trophic food chains, detritus, decomposers, and decomposer predators demonstrated that decomposers play a totally different role than that previously predicted, with regard to their relationship between nutrient cycling and ecosystem stability. The high flux of nutrients due to efficient decomposition by decomposers increases ecosystem stability. However, moderate levels of ecosystem openness (with movement of materials) can either greatly increase or decrease ecosystem stability. Furthermore, the stability of an ecosystem peaks at intermediate openness because open systems are less stable than closed systems. These findings suggest that decomposers and the food‐web dynamics of brown‐world interactions are crucial for ecosystem stability, and that the properties of decomposition rate and openness are important in predicting changes in ecosystem stability in response to changes in decomposition efficiency driven by climate change. 相似文献
997.
G-protein-coupled receptors (GPCRs) are currently the most important pharmaceutical targets for drug discovery because they regulate a wide variety of physiological processes. Consequently, simple and convenient detection systems for ligands that regulate the function of GPCR have attracted attention as powerful tools for new drug development. We previously developed a yeast-based fluorescence reporter ligand detection system using flow cytometry. However, using this conventional detection system, fluorescence from a cell expressing GFP and responding to a ligand is weak, making detection of these cells by fluorescence microscopy difficult. We here report improvements to the conventional yeast fluorescence reporter assay system resulting in the development of a new highly-sensitive fluorescence reporter assay system with extremely bright fluorescence and high signal-to-noise (S/N) ratio. This new system allowed the easy detection of GPCR signaling in yeast using fluorescence microscopy. Somatostatin receptor and neurotensin receptor (implicated in Alzheimer’s disease and Parkinson’s disease, respectively) were chosen as human GPCR(s). The facile detection of binding to these receptors by cognate peptide ligands was demonstrated. In addition, we established a highly sensitive ligand detection system using yeast cell surface display technology that is applicable to peptide screening, and demonstrate that the display of various peptide analogs of neurotensin can activate signaling through the neurotensin receptor in yeast cells. Our system could be useful for identifying lead peptides with agonistic activity towards targeted human GPCR(s). 相似文献
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999.
Toyoaki Ishikura Sumiyo Oue Tokuo Itoh Akihiko Nomura Tohru Ueda Yoshihisa Mizuno 《Nucleosides, nucleotides & nucleic acids》2013,32(4):413-422
Abstract Several types of 3-deazaadenine pentofuranosides, represented by 9-(3-deoxy-β-D-glycero-pent-3-enofuranosyl)-3-deazaadenine (1), 9-(5-deoxy-β-Q-erythro-pent-4-enofuranosyl)-3-deazaadenine (2) and 9-β-D-xylo-furanosyl-3-deazaadenine (3), were prepared starting from 6-chloro-9-β-D-ribofuranosyl-3-deazaadenine (4). 相似文献
1000.
Fumie Yamashita Koichi Azuma Tsukasa Yoshida Kazuhiko Yamada Akihiko Kawahara Satoshi Hattori Hiroaki Takeoka Yoshiaki Zaizen Tomotaka Kawayama Masayoshi Kage Tomoaki Hoshino 《PloS one》2013,8(8)