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991.
The use of 9 pollen sampling sites and 56 14C dates has identified hitherto unsuspected or poorly-defined sequences of mid- to late Holocene (late Neolithic to post-Medieval) anthropogenic vegetation changes in south Cumbria, U.K. A series of small-scale, but significant woodland clearance episodes are recorded throughout the Bronze Age, followed by a marked recession in activity during the early Iron Age. The late Iron Age-Roman periods witnessed the first major clearance of woodland in the region which was succeeded by woodland regeneration in the post-Roman/early Medieval period. Woodland clearance intensified in the later Medieval period culminating in large areas of permanently open landscape. The results show that high-resolution, independently date pollen analysis is necessary to reveal regional evidence of small, temporary Bronze Age clearances. A well-documented prehistoric wooden trackway from Foulshaw Moss is shown to be significantly older than previously thought, dating to the mid-Bronze Age, ca. 1550–1250 cal B.C. Pre-Roman cereal cultivation in the area is also confirmed.The Department of Earth Sciences 相似文献
992.
Anjana Radhakrishnan Chelsea M. Brown Collette S. Guy Charlotte Cooper Raul Pacheco-Gomez Phillip J. Stansfeld Elizabeth Fullam 《MedChemComm》2022,13(10):1225
Tuberculosis, caused by Mycobacterium tuberculosis, claims ∼1.5 million lives annually. Effective chemotherapy is essential to control TB, however the emergence of drug-resistant strains of TB have seriously threatened global attempts to control and eradicate this deadly pathogen. Trehalose recycling via the LpqY-SugABC importer is essential for the virulence and survival of Mtb and inhibiting or hijacking this transport system is an attractive approach for the development of novel anti-tubercular and diagnostic agents. Therefore, we interrogated the drug-like compounds in the open-source Medicines for Malaria Pathogen Box and successfully identified seven compounds from the TB, kinetoplastids and reference compound disease sets that recognise LpqY. The molecules have diverse chemical scaffolds, are not specific trehalose analogues, and may be used as novel templates to facilitate the development of therapeutics that kill Mtb with a novel mechanism of action via the mycobacterial trehalose LpqY-SugABC transport system.Interrogation of the Pathogen Box identified diverse chemical scaffolds against the mycobacterial trehalose transporter. 相似文献
993.
994.
Hamelin ME Yim K Kuhn KH Cragin RP Boukhvalova M Blanco JC Prince GA Boivin G 《Journal of virology》2005,79(14):8894-8903
Human metapneumovirus (hMPV) is a newly described member of the Paramyxoviridae family causing acute respiratory tract infections, especially in young children. We studied the pathogenesis of this viral infection in two experimental small animal models (BALB/c mice and cotton rats). Significant viral replication in the lungs of both animals was found following an intranasal challenge of 10(8) 50% tissue culture infectious doses (TCID50) and persisted for <2 and <3 weeks in the case of cotton rats and mice, respectively. Peak viral loads were found on day 5 postinfection in both mice (mean of 1.92 x 10(7) TCID50/g lung) and cotton rats (mean of 1.03 x 10(5) TCID50/g). Clinical symptoms consisting of breathing difficulties, ruffled fur, and weight loss were noted in mice only around the time of peak viral replication. Most significant pulmonary inflammatory changes and peak expression of macrophage inflammatory protein 1alpha, gamma interferon, and RANTES occurred at the time of maximal viral replication (day 5) in both models. Cellular infiltration occurred predominantly around and within alveoli and persisted for at least 21 days in mice, whereas it was more limited in time with more peribronchiolitis in cotton rats. Both animal models would be of great value in evaluating different therapeutic agents, as well as vaccine candidates against hMPV. 相似文献
995.
The interactive effects of increased carbon dioxide (CO2) concentration and ultraviolet-B (UV-B, 280–320 nm) radiation on Acacia karroo Hayne, a C3 tree, and Themeda triandra Forsk., a C4 grass, were investigated. We tested the hypothesis that A. karroo would show greater CO2-induced growth stimulation than T. triandra, which would partially explain current encroachment of A. karroo into C4 grasslands, but that increased UV-B could mitigate this advantage. Seedlings were grown in open-top chambers in a greenhouse in ambient (360 μmol mol-1) and elevated (650 μmol mol-1) CO2, combined with ambient (1.56 to 8.66 kJ m-2 day-1) or increased (2.22 to 11.93 kJ m-2 day-1) biologically effective (weighted) UV-B irradiances. After 30 weeks, elevated CO2 had no effect on biomass of A. karroo, despite increased net CO2 assimilation rates. Interaction between UV-B and CO2 on stomatal conductance was found, with conductances decreasing only where elevated CO2 and UV-B were supplied separately. Increases in water use efficiencies, foliar starch concentrations, root nodule numbers and total nodule mass were measured in elevated CO2. Elevated UV-B caused only an increase in foliar carbon concentrations. In T. triandra, net CO2 assimilation rates were unaffected in elevated CO2, but stomatal conductances and foliar nitrogen concentrations decreased, and water use efficiencies increased. Biomass of all vegetative fractions, particularly leaf sheaths, was increased in elevated CO2. and was accompanied by increased leaf blade lengths and individual leaf and leaf sheath masses. However, tiller numbers were reduced in elevated CO2. Significantly moderating effects of elevated UV-B were apparent only in individual masses of leaf blades and sheaths, and in total sheath and shoot biomass. The direct CO2-induced growth responses of the species therefore do not support the hypothesis of CO2-driven woody encroachment of C4 grasslands. Rather, differential changes in resource use efficiency between grass and woody species, or morphological responses of grass species, could alter the competitive balance. Increased UV-B radiation is unlikely to substantially alter the CO2 response of these species. 相似文献
996.
997.
Key physiological functions of the intestine are governed by nerves and neurotransmitters. This complex control relies on two neuronal systems: an extrinsic innervation supplied by the two branches of the autonomic nervous system and an intrinsic innervation provided by the enteric nervous system. As a result of constant exposure to commensal and pathogenic microflora, the intestine developed a tightly regulated immune system. In this review, we cover the current knowledge on the interactions between the gut innervation and the intestinal immune system. The relations between extrinsic and intrinsic neuronal inputs are highlighted with regards to the intestinal immune response. Moreover, we discuss the latest findings on mechanisms underlying inflammatory neural reflexes and examine their relevance in the context of the intestinal inflammation. Finally, we discuss some of the recent data on the identification of the gut microbiota as an emerging player influencing the brain function. 相似文献
998.
Barry D. Smith Katherine R. Hagmeier W. Sean Boyd Neil K. Dawe Terri D. Martin Guy L. Monty 《The Journal of wildlife management》2012,76(3):593-599
We used a robust dataset of count and mark-resighting data for Pacific black brant from 1989–2004, and a novel mark-recapture model capable of analyzing such data, to calculate the annual variability and timing of brant as they migrated through the Parksville–Qualicum Beach area, a traditional spring staging site in coastal British Columbia, Canada. Our analysis indicated that the date of departure from this site to northern breeding sites advanced between 10 and 20 days over this period because of a combination of earlier arrival and shorter residence times. Given this change in migration behavior, and the potential implications for population dynamics, we recommend that targeted research on brant wintering, migration, and reproductive strategies should be examined within a greater Pacific-wide context. In this way, the consequences of proximate factors (e.g., disturbance, food, and climate) can be understood in terms of individual fitness and population dynamics. Finally, at the local level, conservation actions are needed to ensure the long term sustainability of Parksville–Qualicum Beach as an important spring staging site for Pacific black brant. © 2011 The Wildlife Society. 相似文献
999.
Influence of White Clover Mosaic Potexvirus Infection on the Endogenous Cytokinin Content of Bean 总被引:1,自引:0,他引:1 下载免费PDF全文
Sean Francis Clarke Marian Jane McKenzie David John Burritt Paul Leslie Guy Paula Elizabeth Jameson 《Plant physiology》1999,120(2):547-552
The cytokinin content in the primary leaves of bean (Phaseolus vulgaris) was monitored for 10 d after inoculation with white clover mosaic potexvirus. The cytokinins were isolated, purified, separated by high-performance liquid chromatography, and quantified by radioimmunoassay. The cytokinins detected at the time of inoculation (d 0) were: (a) the free bases, zeatin (Z), dihydrozeatin (DZ), and isopentenyladenine; (b) the riboside, DZ riboside (DZR); (c) the O-glucosides of DZ, DZR, and Z riboside; (d) the nucleotides, Z riboside-5′-monophosphate and isopentenyladenosine-5′-monophosphate; and (e) trace amounts of Z-9-glucoside and DZ-9-glucoside. During the 10 d after inoculation with white clover mosaic potexvirus, marked quantitative changes in this cytokinin profile were observed. The concentration of the free bases and DZR decreased, accompanied by an increase in the 9-glucosides and the nucleotides. Virus titer increased rapidly 3 d after inoculation, attaining a maximum level at d 5. This increase coincided with the increases in the 9-glucosides and the nucleotides. We propose that the decline in the cytokinin free bases and riboside may allow the increase of virus titer in bean and lead to the senescence of infected leaves. 相似文献
1000.
Oana I. Stanisor Sophie A. van Diest Zhumei Yu Olaf Welting Noor Bekkali Jing Shi Wouter J. de Jonge Guy E. Boeckxstaens Rene M. van den Wijngaard 《PloS one》2013,8(6)