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61.
Covadonga Orejas Sergio Rossi Àurea Peralba Eva García Josep Maria Gili Heike Lippert 《Polar Biology》2013,36(1):61-72
Obelia dichotoma is a thecate hydroid with a worldwide distribution, occurring mainly on shallow water hard substrates. Since the trophic ecology of hydroids in polar waters is badly understood, the aim of the present work was to study qualitatively and quantitatively the diet of these organisms in an Arctic environment and to determine their trophic significance. For this purpose, the density of the hydroid population was documented, and simultaneously, zooplankton was sampled in two different years (1997 and 1998). Prey capture rates were estimated by analysing the gastrovascular content of the polyps in a diurnal cycle. Additionally, the digestion time of O. dichotoma was measured by laboratory feeding experiments using diatoms as food items. The analyses of the gastrovascular cavities of the polyps sampled during the diurnal cycles showed that O. dichotoma fed mainly on faecal pellets, organic matter and microalgae. Zooplankton prey was also observed, but gastrovascular contents and zooplankton abundance did not show any correlation in both years. The consumption rates of the hydroid populations differed between the 2 years. It was almost double (8.9 mg Carbon m?2) in 1998 compared to 1997 (5.5 mg Carbon m?2). The significance of the environmental variability in the feeding ecology and population dynamics of hydroids under Arctic conditions is discussed. 相似文献
62.
Shpilman M Niv-Spector L Katz M Varol C Solomon G Ayalon-Soffer M Boder E Halpern Z Elinav E Gertler A 《The Journal of biological chemistry》2011,286(6):4429-4442
Leptin is a pleiotropic hormone acting both centrally and peripherally. It participates in a variety of biological processes, including energy metabolism, reproduction, and modulation of the immune response. So far, structural elements affecting leptin binding to its receptor remain unknown. We employed random mutagenesis of leptin, followed by selection of high affinity mutants by yeast surface display and discovered that replacing residue Asp-23 with a non-negatively charged amino acid leads to dramatically enhanced affinity of leptin for its soluble receptor. Rational mutagenesis of Asp-23 revealed the D23L substitution to be most effective. Coupling the Asp-23 mutation with alanine mutagenesis of three amino acids (L39A/D40A/F41A) previously reported to convert leptin into antagonist resulted in potent antagonistic activity. These novel superactive mouse and human leptin antagonists (D23L/L39A/D40A/F41A), termed SMLA and SHLA, respectively, exhibited over 60-fold increased binding to leptin receptor and 14-fold higher antagonistic activity in vitro relative to the L39A/D40A/F41A mutants. To prolong and enhance in vivo activity, SMLA and SHLA were monopegylated mainly at the N terminus. Administration of the pegylated SMLA to mice resulted in a remarkably rapid, significant, and reversible 27-fold more potent increase in body weight (as compared with pegylated mouse leptin antagonist), because of increased food consumption. Thus, recognition and mutagenesis of Asp-23 enabled construction of novel compounds that induce potent and reversible central and peripheral leptin deficiency. In addition to enhancing our understanding of leptin interactions with its receptor, these antagonists enable in vivo study of the role of leptin in metabolic and immune processes and hold potential for future therapeutic use in disease pathologies involving leptin. 相似文献
63.
Enrique Isla Dieter Gerdes Sergio Rossi Ida Fiorillo Elisabet Sa?�� Josep-Maria Gili Wolf E. Arntz 《Polar Biology》2011,34(8):1125-1133
Biochemical characteristics of seafloor sediment off Austasen in the southeastern Weddell Sea were assayed in samples recovered
in the early autumn and late spring of 2000 and 2003, respectively. Sediment was separated in the grain-size fractions >200 μm
and <200 μm to distinguish biochemical characteristics in the fraction available for benthic suspension feeders (<200 μm).
In the bulk sediment, the lipid (LPD) and carbohydrate (CHO) contents were significantly different between seasons with higher
LPD content in the early autumn and higher CHO content in the late spring. In the grain-size fractions <200 μm, the LPD and
protein (PRT) contents were significantly higher in the early autumn meaning that in this season the fraction available for
benthic suspension feeders presented higher nutritive value. The relatively higher CHO concentrations observed in each fraction
in the late spring were attributed to refractory matter, whereas the higher PRT and LPD concentrations found during the early
autumn were associated with planktonic material settled after the summer phytoplankton bloom. Our results suggest that there
is seasonal variation in the composition of organic matter in the sediment, with better nutritive quality in the early autumn,
especially in the grain-size fraction available for benthic suspension feeders. These variations also suggest that the benthic
community exploits the fresh organic matter accumulated after the summer throughout the Antarctic dark months leaving the
sediment almost exhaust of LPD and with higher CHO contents, presumably of refractory nature, at the onset of the seasonal
phytoplankton bloom of the following year. 相似文献
64.
The Biology and Economics of Coral Growth 总被引:1,自引:0,他引:1
Osinga R Schutter M Griffioen B Wijffels RH Verreth JA Shafir S Henard S Taruffi M Gili C Lavorano S 《Marine biotechnology (New York, N.Y.)》2011,13(4):658-671
To protect natural coral reefs, it is of utmost importance to understand how the growth of the main reef-building organisms—the
zooxanthellate scleractinian corals—is controlled. Understanding coral growth is also relevant for coral aquaculture, which
is a rapidly developing business. This review paper provides a comprehensive overview of factors that can influence the growth
of zooxanthellate scleractinian corals, with particular emphasis on interactions between these factors. Furthermore, the kinetic
principles underlying coral growth are discussed. The reviewed information is put into an economic perspective by making an
estimation of the costs of coral aquaculture. 相似文献
65.
Kogan Y Halevi-Tobias KE Hochman G Baczmanska AK Leyns L Agur Z 《The Biochemical journal》2012,444(1):115-125
The Wnt signalling pathway controls cell proliferation and differentiation, and its deregulation is implicated in different diseases including cancer. Learning how to manipulate this pathway could substantially contribute to the development of therapies. We developed a mathematical model describing the initial sequence of events in the Wnt pathway, from ligand binding to β-catenin accumulation, and the effects of inhibitors, such as sFRPs (secreted Frizzled-related proteins) and Dkk (Dickkopf). Model parameters were retrieved from experimental data reported previously. The model was retrospectively validated by accurately predicting the effects of Wnt3a and sFRP1 on β-catenin levels in two independent published experiments (R(2) between 0.63 and 0.91). Prospective validation was obtained by testing the model's accuracy in predicting the effect of Dkk1 on Wnt-induced β-catenin accumulation (R(2)≈0.94). Model simulations under different combinations of sFRP1 and Dkk1 predicted a clear synergistic effect of these two inhibitors on β-catenin accumulation, which may point towards a new treatment avenue. Our model allows precise calculation of the effect of inhibitors applied alone or in combination, and provides a flexible framework for identifying potential targets for intervention in the Wnt signalling pathway. 相似文献
66.
Maria-J. Uriz Josep-Maria Gili Covadonga Orejas Alicia-R. Perez-Porro 《Polar Biology》2011,34(2):243-255
Sponges are the dominant invertebrates in many Antarctic communities, where they play a decisive structural function thanks
to their abundance and large sizes. However, current knowledge on Antarctic sponges remains poor even with respect to basic
aspects such as taxonomy. Here, we report on an Antarctic species of the genus Stylocordyla, which has been recorded for a long time under the name of the boreal S. borealis due to spicule and growth habit similarities. A thorough study of dense populations of the only Stylocordyla species known up to now from the eastern zone of the Weddell Sea as well as the re-examination of several specimens (including
the type material) of S. borealis has allowed us to assess the variability of the boreal species and to confirm that the austral species is not S. borealis (Lovén, 1868) but a new species of Stylocordyla, different from the other congeners recorded from southern latitudes. The new species S. chupachups commonly dwells on horizontal or slighted sloped hard bottoms of the continental shelf of Weddell Sea, from 100 m to below
400 m depth, although the densest populations usually occur between 150 and 300 m. It is a pioneer species in areas that have
been scoured by icebergs, and thus its presence may be considered an indicator of recent colonisation. 相似文献
67.
68.
Pedro Gili Alfredo MederosEduardo Medina de la Rosa Alfonso Muñoz 《Inorganica chimica acta》2002,331(1):16-24
A computational study of chromium(VI) and (V) peroxides, which exhibit important genotoxic and mutagenic activity, is reported. Energies and equilibrium geometries for [CrVI(O)(O2)2(OH)]−, [CrVI(O)(O2)2(OH2)], [CrVI(O)(O2)2(py)], [CrVI(OH)(O2)2(OH2)]+, [CrV(O)(O2)2(OH2)]− and species were calculated using molecular mechanics calculations (MMFF94 and MM+), quantum calculations with semi-empirical methods (RHF and UHF/PM3) and density functional theory (pBP86/DN* or pBP/DN* and B3LYP/6-31G(d). Equilibrium geometries for the compounds [CrV(O2)3(OH)]2− and [CrV(O2)4]3− were determined by molecular mechanics. Vibrational frequencies, standard thermodynamic quantities and electronic spectra were calculated using B3LYP/6-31G(d). The structural relationship between all these species and an explanation of the formation of peroxo species in the acid-basic pH range are given. An experimental study of peroxo species in basic medium was also performed (synthesis, X-ray powder diffraction patterns and infrared spectra of the peroxo complexes isolated) but did not confirm the existence of a tri-peroxo complex in the solid phase. 相似文献
69.
Ecosystems of the Mediterranean region are characterized by a heterogeneous and dynamic landscape mosaic of vegetation formations
that provide diverse benefits: agro pastoral products, ecosystem services, and other utilities. Valuation of these benefits
in different states of the ecosystem is an important step towards conservation, decision making, and land management. Yet,
studies of this kind are scarce, especially cases dealing with more than one benefit. Multiple benefits evaluation is not
straightforward; it involves many difficulties and questions which have no agreed solutions, e.g. estimation, common currency,
and optimal solution. In this study we present a methodology for the estimation of three benefits in different components
of Mediterranean woody vegetation in Israel. Densities of geophyte wildflowers, honey flowers, and fleshy fruits as food for
birds were measured within five vegetation components defined by dominant plant functional types, in four sites with different
disturbance histories. Each benefit was measured in its own units. The results showed significant differences between vegetation
states in values of each benefit. Therefore, it is possible to calculate the contributions of different cover components for
these three benefits. Furthermore, this indicates that it is possible to estimate the level of benefits at larger scales as
a first approximation, by considering only the composition of the vegetation cover. The values for the three benefits were
standardized to illustrate the question of multiple benefits valuation. This method does not lead to an optimization, but
can nevertheless provide a useful tool toward conservation and rational management by land managers and policy makers. 相似文献
70.
Ravid Shechter Anat London Chen Varol Catarina Raposo Melania Cusimano Gili Yovel Asya Rolls Matthias Mack Stefano Pluchino Gianvito Martino Steffen Jung Michal Schwartz 《PLoS medicine》2009,6(7)