The timing of life-history events in a changing climate.
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Although empirical and theoretical studies suggest that climate influences the timing of life-history events in animals and plants, correlations between climate and the timing of events such as egg-laying, migration or flowering do not reveal the mechanisms by which natural selection operates on life-history events. We present a general autoregressive model of the timing of life-history events in relation to variation in global climate that, like autoregressive models of population dynamics, allows for a more mechanistic understanding of the roles of climate, resources and competition. We applied the model to data on 50 years of annual dates of first flowering by three species of plants in 26 populations covering 4 degrees of latitude in Norway. In agreement with earlier studies, plants in most populations and all three species bloomed earlier following warmer winters. Moreover, our model revealed that earlier blooming reflected increasing influences of resources and density-dependent population limitation under climatic warming. The insights available from the application of this model to phenological data in other taxa will contribute to our understanding of the roles of endogenous versus exogenous processes in the evolution of the timing of life-history events in a changing climate. (+info)
Neuroprotective and antioxidant effects of the ethyl acetate fraction prepared from Tussilago farfara L.
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The flower buds of Tussilago farfara L. (Compositae) have been traditionally used in Oriental medicine for the treatment of bronchitis and asthma. The extract of T. farfara was reported to exhibit antiinflammatory actions by inhibiting arachidonic acid metabolism and nitric oxide (NO) production in lipopolysaccharide-activated macrophages. In the present study, we investigated the effects of the ethyl acetate (EA) fraction on various types of neuronal cell damage induced in primary cultured rat cortical cells. Its antioxidant activities were also evaluated by cell-free bioassays. We found that the EA fraction potently inhibited the neuronal damage induced by arachidonic acid. We also found that it significantly attenuated the neuronal damage induced by spermine NONOate, a stable NO generator. In addition, it inhibited the A(beta(25-35))-induced neurotoxicity and glutamate- or N-methyl-D-aspartic acid-induced excitotoxicity. It was found that the oxidative neuronal damage induced by H2O2, xanthine/xanthine oxidase, or Fe(2+)/ascorbic acid was also inhibited by the EA fraction. Furthermore, it was shown to inhibit lipid peroxidation initiated by Fe(2+)/ascorbic acid in rat brain homogenates, and scavenge DPPH radicals. This is the first demonstration of neuroprotective and antioxidant effects of T. farfara. Although complex mechanisms may be involved in the neuroprotective actions, T. farfara may be useful for the management of neurodegenerative disorders associated with inflammation, A(beta), excitotoxicity, and/or oxidative stress. (+info)
Methylophilus flavus sp. nov. and Methylophilus luteus sp. nov., aerobic, methylotrophic bacteria associated with plants.
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