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91.
The distributions of many terrestrial organisms are currently shifting in latitude or elevation in response to changing climate. Using a meta-analysis, we estimated that the distributions of species have recently shifted to higher elevations at a median rate of 11.0 meters per decade, and to higher latitudes at a median rate of 16.9 kilometers per decade. These rates are approximately two and three times faster than previously reported. The distances moved by species are greatest in studies showing the highest levels of warming, with average latitudinal shifts being generally sufficient to track temperature changes. However, individual species vary greatly in their rates of change, suggesting that the range shift of each species depends on multiple internal species traits and external drivers of change. Rapid average shifts derive from a wide diversity of responses by individual species. 相似文献
92.
Scheiermann C Meda P Aurrand-Lions M Madani R Yiangou Y Coffey P Salt TE Ducrest-Gay D Caille D Howell O Reynolds R Lobrinus A Adams RH Yu AS Anand P Imhof BA Nourshargh S 《Science (New York, N.Y.)》2007,318(5855):1472-1475
JAM-C is an adhesion molecule that is expressed on cells within the vascular compartment and epithelial cells and, to date, has been largely studied in the context of inflammatory events. Using immunolabeling procedures in conjunction with confocal and electron microscopy, we show here that JAM-C is also expressed in peripheral nerves and that this expression is localized to Schwann cells at junctions between adjoining myelin end loops. Sciatic nerves from JAM-C-deficient [having the JAM-C gene knocked out (KO)] mice exhibited loss of integrity of the myelin sheath and defective nerve conduction as indicated by morphological and electrophysiological studies, respectively. In addition, behavioral tests showed motor abnormalities in the KO animals. JAM-C was also expressed in human sural nerves with an expression profile similar to that seen in mice. These results demonstrate that JAM-C is a component of the autotypic junctional attachments of Schwann cells and plays an important role in maintaining the integrity and function of myelinated peripheral nerves. 相似文献
93.
O'Doherty J Dayan P Schultz J Deichmann R Friston K Dolan RJ 《Science (New York, N.Y.)》2004,304(5669):452-454
Instrumental conditioning studies how animals and humans choose actions appropriate to the affective structure of an environment. According to recent reinforcement learning models, two distinct components are involved: a "critic," which learns to predict future reward, and an "actor," which maintains information about the rewarding outcomes of actions to enable better ones to be chosen more frequently. We scanned human participants with functional magnetic resonance imaging while they engaged in instrumental conditioning. Our results suggest partly dissociable contributions of the ventral and dorsal striatum, with the former corresponding to the critic and the latter corresponding to the actor. 相似文献
94.
Jacobs Z Roberts RG Galbraith RF Deacon HJ Grün R Mackay A Mitchell P Vogelsang R Wadley L 《Science (New York, N.Y.)》2008,322(5902):733-735
The expansion of modern human populations in Africa 80,000 to 60,000 years ago and their initial exodus out of Africa have been tentatively linked to two phases of technological and behavioral innovation within the Middle Stone Age of southern Africa-the Still Bay and Howieson's Poort industries-that are associated with early evidence for symbols and personal ornaments. Establishing the correct sequence of events, however, has been hampered by inadequate chronologies. We report ages for nine sites from varied climatic and ecological zones across southern Africa that show that both industries were short-lived (5000 years or less), separated by about 7000 years, and coeval with genetic estimates of population expansion and exit times. Comparison with climatic records shows that these bursts of innovative behavior cannot be explained by environmental factors alone. 相似文献
95.
96.
Production of C2H4, but not of CH4, was observed in anoxically incubated soil samples (cambisol on loamy sand) from a deciduous forest. Ethylene production was prevented by autoclaving, indicating its microbial origin. Ethylene production gradually decreased from 4 to 12 cm soil depth and was not affected by moisture or addition of methionine, a possible precursor of C2H4. Oxidation of atmospheric CH4 in soil samples was inhibited by C2H4. Ethylene concentrations of 3, 6 and 10 μl l−1 decreased CH4 uptake by 21, 63 and 98%, respectively. Methionine and methanethiol, a possible product of methionine degradation, also inhibited CH4 oxidation. Under oxic conditions, C2H4 was consumed in the soil samples. Ethylene oxidation kinetics exhibited two apparent Km values of 40 μl l−1 and 12,600 μl l−1 suggesting the presence of two different types of C2H4-oxidizing microorganisms. Methanotrophic bacteria were most probably not responsible for C2H4 oxidation, since the maximum of C2H4 oxidation activity was localized in soil layers (2-8 cm depth) above those (8-10 cm depth) of CH4 oxidation activity. Our observations suggest that C2H4 production in the upper soil layers inhibits CH4 oxidation, thus being one reason for the localization of methanotrophic activity in deeper soil layers. 相似文献
97.
Maillard reaction products inhibit oxidation of human low-density lipoproteins in vitro 总被引:2,自引:0,他引:2
Dittrich R El-Massry F Kunz K Rinaldi F Peich CC Beckmann MW Pischetsrieder M 《Journal of agricultural and food chemistry》2003,51(13):3900-3904
Dietary intake of antioxidants has been associated with a reduced risk of cardiovascular diseases, which is very likely caused by their capability of prevent oxidation of low-density lipoproteins (LDL). During food processing and storage, substances with antioxidative properties are formed by Maillard reactions. In this study, the activity of Maillard products to inhibit copper-induced oxidation of human LDL in vitro was investigated. d-Glucose was heated with an equimolar amount of glycine, l-lysine, or l-arginine, for 1 h under reflux. The increase of the antioxidative activity (AOA) of the Maillard mixtures was highly significant compared to the control mixtures. Additionally, two defined Maillard products with amino reductone structure were tested. 3-Hydroxy-4-(morpholino)-3-buten-2-one (1) and amino hexose reductone (2) showed a significant and dose dependent AOA. Compound 1 was about half as active as ascorbic acid, which served as positive control. Thus, it can be concluded that Maillard products, particularly those with amino reductone structure, have the strong potential to inhibit LDL oxidation. 相似文献
98.
The initial dynamic flavor release from sucrose solutions was modeled. Modeling was based on the theoretical hydration behavior of sucrose, theoretical physicochemical data of flavor volatiles, and process parameters of a headspace apparatus used for model validation. The rate-limiting factor determining the initial flavor release was the hydration of sucrose, which in turn depends on the molarity of sucrose in the solution and, therefore, on the actual amount of nonbound water. Improved solubility of the more hydrophilic compounds due to their orientation toward the hydration shells of the sugar molecules was considered. The viscosity of nonassociated water forming the microregion for mass transfer of volatiles was considered instead of the bulk solution viscosity. Experimental validation of the model by real-time measurements of dynamic flavor release using foodlike flavor concentrations confirmed the above theory. Increasing sucrose concentrations resulted predominantly in increased flavor release, and bulk solution viscosity showed no effect. 相似文献
99.
Leite da Silva Wilian Aparecido Poehland Ralf Carvalho de Oliveira Caroline Ribeiro Ferreira Mariane Gabriela Cesar Garcia de Almeida Ricardo Cáceres Mirela Brochado Souza Macedo Gustavo Guerino da Costa e Silva Eliane Vianna Alves Fabiana Villa Nogueira Eriklis de Andrade Melo-Sterza Fabiana 《Tropical animal health and production》2020,52(5):2273-2281
Tropical Animal Health and Production - The aim of this study was to evaluate the impact of increased shadow supply in integrated crop-livestock-forest systems on in vitro embryonic development and... 相似文献
100.