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101.
Exhaustion of a natural resource stock may be a rational choice for an individual and/or a community, even if a sustainable
use for the resource is feasible and the resource users are farsighted and well informed on the ecosystem. We identify conditions
under which it is optimal not to sustain resource use. These conditions concern the discounting of future benefits, instability
of a social system or ecosystem, nonconvexity of natural growth function, socio-psychological value of employment, and strategic
interaction among resource users. The identification of these conditions can help design policies to prevent unsustainable
patterns of resource use.
相似文献
102.
Ossama B. Kashlan Brandon M. Blobner Zachary Zuzek Michael Tolino Thomas R. Kleyman 《The Journal of biological chemistry》2015,290(1):568-576
The epithelial Na+ channel (ENaC) has a key role in the regulation of extracellular fluid volume and blood pressure. ENaC belongs to a family of ion channels that sense the external environment. These channels have large extracellular regions that are thought to interact with environmental cues, such as Na+, Cl−, protons, proteases, and shear stress, which modulate gating behavior. We sought to determine the molecular mechanism by which ENaC senses high external Na+ concentrations, resulting in an inhibition of channel activity. Both our structural model of an ENaC α subunit and the resolved structure of an acid-sensing ion channel (ASIC1) have conserved acidic pockets in the periphery of the extracellular region of the channel. We hypothesized that these acidic pockets host inhibitory allosteric Na+ binding sites. Through site-directed mutagenesis targeting the acidic pocket, we modified the inhibitory response to external Na+. Mutations at selected sites altered the cation inhibitory preference to favor Li+ or K+ rather than Na+. Channel activity was reduced in response to restraining movement within this region by cross-linking structures across the acidic pocket. Our results suggest that residues within the acidic pocket form an allosteric effector binding site for Na+. Our study supports the hypothesis that an acidic cleft is a key ligand binding locus for ENaC and perhaps other members of the ENaC/degenerin family. 相似文献
103.
The interaction between plants and pathogens represents a dynamic competition between a robust immune system and efficient infectious strategies. Plant innate immunity is composed of complex and highly regulated molecular networks, which can be triggered by the perception of either conserved or race‐specific pathogenic molecular signatures. Small RNAs are emerging as versatile regulators of plant development, growth and response to biotic and abiotic stresses. They act in different tiers of plant immunity, including the pathogen‐associated molecular pattern‐triggered and the effector‐triggered immunity. On the other hand, pathogens have evolved effector molecules to suppress or hijack the host small RNA pathways. This leads to an arms race between plants and pathogens at the level of small RNA‐mediated defense.Here, we review recent advances in small RNA‐mediated defense responses and discuss the challenging questions in this area. 相似文献
104.
Paul B. Chapman Stephen D. Gillies Alan N. Houghton Regina M. Reilly 《Cancer immunology, immunotherapy : CII》1994,39(3):198-204
R24, a mouse monoclonal antibody against GD3 ganglioside, exhibits a wide range of in vitro effector functions. It also has the ability to bind to itself, presumably through homophilic Fab-Fab interactions, which have been proposed to contribute to its high relative avidity for GD3 and to its effector function activity. It is not known which of these characteristics is necessary for the antitumor effects observed in melanoma patients treated with R24. A mouse-human chimeric R24 (chR24) molecule has been constructed in which the GD3-binding site is preserved. Chimeric R24 demonstrates a lower level of binding to GD3 than does mouse R24 suggesting that there may be some differences between the GD3-binding sites of the two mAb or that Fc determinants can contribute to R24 avidity for GD3. The property of homophilic binding is retained by chR24, demonstrating formally that homophilic binding of R24 involves interactions between variable domains. Both R24 and chR24 fix human complement and mediate antibody-dependent cellular cytotoxicity although chR24 was slightly less efficient at the latter. Unlike R24, chR24 was not able to inhibit melanoma cell attachment to plastic surfaces and was not able to activate human T lymphocytes. We hypothesize that chR24 does not bind to GD3 with an avidity high enough to mediate these effector functions.Supported by Public Health Service grants PO1-CA33049 and RO1-CA57363 相似文献
105.
The chaperone Lhs1 contributes to the virulence of the fish-pathogenic oomycete Aphanomyces invadans
《Fungal biology》2020,124(12):1024-1031
Oomycetes are fungal-like eukaryotes and many of them are pathogens that threaten natural ecosystems and cause huge financial losses for the aqua- and agriculture industry. Amongst them, Aphanomyces invadans causes Epizootic Ulcerative Syndrome (EUS) in fish which can be responsible for up to 100% mortality in aquaculture. As other eukaryotic pathogens, in order to establish and promote an infection, A. invadans secretes proteins, which are predicted to overcome host defence mechanisms and interfere with other processes inside the host. We investigated the role of Lhs1 which is part of an ER-resident complex that generally promotes the translocation of proteins from the cytoplasm into the ER for further processing and secretion. Interestingly, proteomic studies reveal that only a subset of virulence factors are affected by the silencing of AiLhs1 in A. invadans indicating various secretion pathways for different proteins. Importantly, changes in the secretome upon silencing of AiLhs1 significantly reduces the virulence of A. invadans in the infection model Galleriamellonella. Furthermore, we show that AiLhs1 is important for the production of zoospores and their cluster formation. This renders proteins required for protein ER translocation as interesting targets for the potential development of alternative disease control strategies in agri- and aquaculture. 相似文献
106.
107.
This study hypothesized that oxygen uptake (ṀO2) measured with a novel protocol of chasing rainbow trout Oncorhynchus mykiss to exhaustion inside a static respirometer while simultaneously monitoring ṀO2 (ṀO2chase) would generate the same and repeatable peak value as when peak active ṀO2 (ṀO2active) is measured in a critical swimming speed protocol. To reliably determine peak ṀO2chase, and compare to the peak during recovery of ṀO2 after a conventional chase protocol outside the respirometer (ṀO2rec), this study applied an iterative algorithm and a minimum sampling window duration (i.e., 1 min based on an analysis of the variance in background and exercise ṀO2) to account for ṀO2 dynamics. In support of this hypothesis, peak ṀO2active (707 ± 33 mg O2 h−1 kg−1) and peak ṀO2chase (663 ± 43 mg O2 h−1 kg−1) were similar (P = 0.49) and repeatable (Pearson's and Spearman's correlation test; r ≥ 0.77; P < 0.05) when measured in the same fish. Therefore, estimates of ṀO2max can be independent of whether a fish is exhaustively chased inside a respirometer or swum to fatigue in a swim tunnel, provided ṀO2 is analysed with an iterative algorithm and a minimum but reliable sampling window. The importance of using this analytical approach was illustrated by peak ṀO2chase being 23% higher (P < 0.05) when compared with a conventional sequential interval regression analysis, whereas using the conventional chase protocol (1-min window) outside the respirometer increased this difference to 31% (P < 0.01). Moreover, because peak ṀO2chase was 18% higher (P < 0.05) than peak ṀO2rec, chasing a fish inside a static respirometer may be a better protocol for obtaining maximum ṀO2. 相似文献
108.
109.
Can Liu Andrew J. Martins William W. Lau Nicholas Rachmaninoff Jinguo Chen Luisa Imberti Darius Mostaghimi Danielle L. Fink Peter D. Burbelo Kerry Dobbs Ottavia M. Delmonte Neha Bansal Laura Failla Alessandra Sottini Eugenia Quiros-Roldan Kyu Lee Han Brian A. Sellers Foo Cheung John S. Tsang 《Cell》2021,184(7):1836-1857.e22
110.
Pregnancy is associated with reduced locomotor performance in several reptile species, but the reasons for this reduction remain unclear. Previous authors generally have assumed that the decreased maternal mobility is due to the physical burden of the clutch, but our data on a viviparous Tasmanian scincid lizard (Niveoscincus microlepidotum) suggest a different interpretation. Running speeds of gravid female skinks decrease during gestation (as litter mass increases), but this locomotor impairment is due to physiological changes associated with pregnancy, rather than simple physical burdening. Maternal running speeds are unrelated to litter masses, and do not increase in the week after parturition. Females with very large abdominal fat‐bodies (due to ad libitum feeding in the laboratory), equivalent in mass to the litter, nonetheless run rapidly. If the locomotor ‘costs’ of reproduction reflect all‐or‐none physiological changes associated with pregnancy, then the magnitude of such costs may correlate only weakly with the actual level of reproductive investment. Because life‐history models predict that the relationship between fecundity and ‘cost’ has important evolutionary consequences, our results highlight the need to clarify the causal basis for locomotor impairment in gravid reptiles. 相似文献