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851.
Evidence that the intestinal microbiota is intrinsically linked with overall health, including cancer risk, is emerging. Moreover, its composition is not fixed but can be influenced by several dietary components. Dietary modifiers, including the consumption of live bacteria (probiotics) and indigestible or limited digestible food constituents such as oligosaccharides (prebiotics) and polyphenols or both (synbiotics), are recognized modifiers of the numbers and types of microbes and have been reported to reduce colon cancer risk experimentally. Microorganisms also have the ability to generate bioactive compounds from food components. Examples include equol from isoflavones, enterodiol and enterolactone from lignans and urolithins from ellagic acid, which have also been demonstrated to retard experimentally induced cancers. The gastrointestinal microbiota can also influence both sides of the energy balance equation, namely, as a factor influencing energy utilization from the diet and as a factor that influences host genes that regulate energy expenditure and storage. Because of the link between obesity and cancer incidence and mortality, this complex complexion deserves greater attention. Overall, a dynamic interrelationship exists between the intestinal microbiota and colon cancer risk, which can be modified by dietary components and eating behaviors. 相似文献
852.
How do elevated CO2 and O3 affect the interception and utilization of radiation by a soybean canopy?
ORLA DERMODY STEPHEN P. LONG†§ KELLY McCONNAUGHAY‡ EVAN H. DeLUCIA †§ 《Global Change Biology》2008,14(3):556-564
Net productivity of vegetation is determined by the product of the efficiencies with which it intercepts light (?i) and converts that intercepted energy into biomass (?c). Elevated carbon dioxide (CO2) increases photosynthesis and leaf area index (LAI) of soybeans and thus may increase ?i and ?c; elevated O3 may have the opposite effect. Knowing if elevated CO2 and O3 differentially affect physiological more than structural components of the ecosystem may reveal how these elements of global change will ultimately alter productivity. The effects of elevated CO2 and O3 on an intact soybean ecosystem were examined with Soybean Free Air Concentration Enrichment (SoyFACE) technology where large field plots (20‐m diameter) were exposed to elevated CO2 (~550 μmol mol?1) and elevated O3 (1.2 × ambient) in a factorial design. Aboveground biomass, LAI and light interception were measured during the growing seasons of 2002, 2003 and 2004 to calculate ?i and ?c. A 15% increase in yield (averaged over 3 years) under elevated CO2 was caused primarily by a 12% stimulation in ?c , as ?i increased by only 3%. Though accelerated canopy senescence under elevated O3 caused a 3% decrease in ?i, the primary effect of O3 on biomass was through an 11% reduction in ?c. When CO2 and O3 were elevated in combination, CO2 partially reduced the negative effects of elevated O3. Knowing that changes in productivity in elevated CO2 and O3 were influenced strongly by the efficiency of conversion of light energy into energy in plant biomass will aid in optimizing soybean yields in the future. Future modeling efforts that rely on ?c for calculating regional and global plant productivity will need to accommodate the effects of global change on this important ecosystem attribute. 相似文献
853.
854.
The ecological significance of toxic nectar 总被引:18,自引:0,他引:18
Lynn S. Adler 《Oikos》2000,91(3):409-420
Although plant-herbivore and plant-pollinator interactions have traditionally been studied separately, many traits are simultaneously under selection by both herbivores and pollinators. For example, secondary compounds commonly associated with herbivore defense have been found in the nectar of many plant species, and many plants produce nectar that is toxic or repellent to some floral visitors. Although secondary compounds in nectar and toxic nectar are geographically and phylogenetically widespread, their ecological significance is poorly understood. Several hypotheses have been proposed for the possible functions of toxic nectar, including encouraging specialist pollinators, deterring nectar robbers, preventing microbial degradation of nectar, and altering pollinator behavior. All of these hypotheses rest on the assumption that the benefits of toxic nectar must outweigh possible costs; however, to date no study has demonstrated that toxic nectar provides fitness benefits for any plant. Therefore, in addition to these adaptive hypotheses, we should also consider the hypothesis that toxic nectar provides no benefits or is tolerably detrimental to plants, and occurs due to previous selection pressures or pleiotropic constraints. For example, secondary compounds may be transported into nectar as a consequence of their presence in phloem, rather than due to direct selection for toxic nectar. Experimental approaches are necessary to understand the role of toxic nectar in plant-animal interactions. 相似文献
855.
Tanner Miest Dyana Saenz Anne Meehan Manuel Llano Eric M. Poeschla 《Methods (San Diego, Calif.)》2009,47(4):298-303
RNAi is a powerful technology for analyzing gene function in human cells. However, its utility can be compromised by inadequate knockdown of the target mRNA or by interpretation of effects without rigorous controls. We review lentiviral vector-based methods that enable transient or stable knockdowns to trace mRNA levels in human CD4+ T cell lines and other targets. Critical controls are reviewed, including rescue of the pre-knockdown phenotype by re-expression of the targeted gene. The time from thinking about a potential knockdown target to analysis of phenotypes can be as short as a few weeks. 相似文献
856.
S. Renaud S. Guillemard M.-C. Eberlé-Pouzeratte C. Lemanski P. Faurous J.-C. Artus 《Médecine Nucléaire》2009,33(7):415-424
ObjectiveTo evaluate the contribution of FDG-PET in the management of anal carcinoma, with special emphasis on its impact on therapeutic strategy.Materials and methodsFrom March 2005 to August 2008, 48 PET were performed on 43 patients with anal epidermoid carcinoma, in initial staging (IS: 20 exams), therapeutic response assessment (TRA: 11), and recurrence assessment (RA: 17). We compared initial therapeutic strategies defined on conventional assessment results, to final ones chosen after PET.ResultsPET revealed lesions that were undetected by conventional investigation in 23% of cases (IS: 25%; TRA: 18%; RA: 23%) and cleared suspicious lesions in 21% of cases (IS: 10%; TRA: 18%; RA: 35%). It influenced the therapeutic strategy, and sometimes even modified it radically, in 44% of cases (IS: 35%; TRA: 54%; RA: 47%). This therapeutic impact was stronger in settings with diagnostic ambiguity, in which PET allowed to specify the diagnosis and to orientate consequently the therapeutic choice.ConclusionPET is interesting in the management of anal carcinoma, especially in uncertain diagnostic settings, in which the metabolic information brought allows to influence the therapeutic choice in almost half of the cases. 相似文献
857.
Dreams are often used to promote religion, or to propagate an interpretation of religion, or to bring political ideas to the fore. A dream can be used as an indication of divine help and thus it is a perfect tool for promoting ideas. Dreams figure in religious propaganda in Christian, Jewish, and Muslim traditions (e.g., in Osama bin Laden's tapes). In classical literature, we find many kings, emperors, or generals who had visions or dreams, especially in association with their accession to power. It is the thesis of this article that in the encounter between Jewish (-Christian) cultures and the Hellenistic world dreams were shared as possible means of divine communication. An important example is the dream in Acts 16,9?10, the most Hellenistic dream of the New Testament. This dream is part of a larger unit, Paul's new move from Asia to Europe. I will try to show that the author of Acts combines here the story of Aeneas (e.g., as told by Virgil) and the story of Jesus, an interesting merging of two cultures. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
858.
859.
Jo-Anne M.D. Murray Catherine Dunnett Meriel J.S. Moore-Colyer Annette C. Longland 《Animal Feed Science and Technology》2012,171(2-4):192-204
A series of in vitro experiments were conducted to assess three fibrolytic enzyme preparations as potential feed additives in equine diets. The three fibrolytic enzyme preparations were a concentrated cellulase (E1), an acid cellulase (E2) and a concentrated xylanase (E3). The enzymes were evaluated on their ability to modify the cell wall fraction of high-temperature dried lucerne (HTL) under various experimental conditions including differences in temperature, pH, incubation period, substrate levels and particle size to enable selection of the enzyme preparation most effective in the hydrolysis of lucerne. Results showed enzyme activities (as measured by reducing sugar assays) to be greatest at 50 °C, pH 5 and over an incubation period of greater than 20 h. E1 exhibited the greatest effect on total monosaccharide release from the HTL compared to E2 and E3. Moreover, dry matter (DM) and total non-starch polysaccharide (TNSP) losses were also greater in HTL treated with E1 compared to E2 and E3. Therefore, since the cell wall fraction of HTL contained substantial amounts of cellulose, the enzyme with the highest cellulase activity (Enzyme 1) was most effective in hydrolysing the cell walls of HTL. Consequently, it would appear that the application of exogenous fibrolytic enzyme preparations to forages requires the chemical characterisation of the target forage to enable selection of enzymes that are (a) most suitable to degrade the cell wall components of the candidate forage and (b) effective under field conditions. 相似文献
860.
The corixid species breeding in temporary rock pools of Baltic archipelago live in a highly fragmented and unpredictable habitat. Shallow rock pools can dry out and be refilled repeatedly during a summer causing high mortality of immatures. In deeper pools, young nymphs face intense competition by older stages including cannibalism. The adult corixids move frequently between rock pools and are thus able to use currently available habitat for reproduction. In this dispersal behaviour, the ability to assess the local population density and hence select the more suitable low density patches would be advantageous. We studied the effect of local population density on the frequency of dispersive flights of Arctocorisa carinata (Sahlberg) and Callicorixa producta (Reuter) experimentally, using rock pools from which nymphs of both species were removed. The dispersal rates of marked C. producta adults were significantly lower from experimental rock pools than from normal density controls, leading to a concentration of C. producta adults in the experimental rock pools. Indications of immigration rate differences between the experimental and control pools were also observed. No clear differences were found in the superior competitor A. carinata. 相似文献