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21.
AB Chang NC Cox J Purcell JM Marchant PJ Lewindon GJ Cleghorn LC Ee GD Withers MK Patrick J Faoagali 《Respiratory research》2005,6(1):1-5
Background and methods
Human metapneumovirus (hMPV) is a recently discovered respiratory virus associated with bronchiolitis, pneumonia, croup and exacerbations of asthma. Since respiratory viruses are frequently detected in patients with acute exacerbations of COPD (AE-COPD) it was our aim to investigate the frequency of hMPV detection in a prospective cohort of hospitalized patients with AE-COPD compared to patients with stable COPD and to smokers without by means of quantitative real-time RT-PCR.Results
We analysed nasal lavage and induced sputum of 130 patients with AE-COPD, 65 patients with stable COPD and 34 smokers without COPD. HMPV was detected in 3/130 (2.3%) AE-COPD patients with a mean of 6.5 × 105 viral copies/ml in nasal lavage and 1.88 × 105 viral copies/ml in induced sputum. It was not found in patients with stable COPD or smokers without COPD.Conclusion
HMPV is only found in a very small number of patients with AE-COPD. However it should be considered as a further possible viral trigger of AE-COPD because asymptomatic carriage is unlikely. 相似文献22.
Donnelly MJ McCall PJ Lengeler C Bates I D'Alessandro U Barnish G Konradsen F Klinkenberg E Townson H Trape JF Hastings IM Mutero C 《Malaria journal》2005,4(1):12-5
There are already 40 cities in Africa with over 1 million inhabitants and the United Nations Environmental Programme estimates that by 2025 over 800 million people will live in urban areas. Recognizing that malaria control can improve the health of the vulnerable and remove a major obstacle to their economic development, the Malaria Knowledge Programme of the Liverpool School of Tropical Medicine and the Systemwide Initiative on Malaria and Agriculture convened a multi-sectoral technical consultation on urban malaria in Pretoria, South Africa from 2nd to 4th December, 2004. The aim of the meeting was to identify strategies for the assessment and control of urban malaria. This commentary reflects the discussions held during the meeting and aims to inform researchers and policy makers of the potential for containing and reversing the emerging problem of urban malaria. 相似文献
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ROBERT R. JUNKER RICHARD BLEIL CURTIS C. DAEHLER NICO BLÜTHGEN 《Ecological Entomology》2010,35(6):760-767
1. Sympatric flower visitor species often partition nectar and pollen and thus affect each other's foraging pattern. Consequently, their pollination service may also be influenced by the presence of other flower visiting species. Ants are solely interested in nectar and frequent flower visitors of some plant species but usually provide no pollination service. Obligate flower visitors such as bees depend on both nectar and pollen and are often more effective pollinators. 2. In Hawaii, we studied the complex interactions between flowers of the endemic tree Metrosideros polymorpha (Myrtaceae) and both, endemic and introduced flower‐visiting insects. The former main‐pollinators of M. polymorpha were birds, which, however, became rare. We evaluated the pollinator effectiveness of endemic and invasive bees and whether it is affected by the type of resource collected and the presence of ants on flowers. 3. Ants were dominant nectar‐consumers that mostly depleted the nectar of visited inflorescences. Accordingly, the visitation frequency, duration, and consequently the pollinator effectiveness of nectar‐foraging honeybees (Apis mellifera) strongly decreased on ant‐visited flowers, whereas pollen‐collecting bees remained largely unaffected by ants. Overall, endemic bees (Hylaeus spp.) were ineffective pollinators. 4. The average net effect of ants on pollination of M. polymorpha was neutral, corresponding to a similar fruit set of ant‐visited and ant‐free inflorescences. 5. Our results suggest that invasive social hymenopterans that often have negative impacts on the Hawaiian flora and fauna may occasionally provide neutral (ants) or even beneficial net effects (honeybees), especially in the absence of native birds. 相似文献
27.
PJ Waller G Bernes L Rudby-Martin B-L Ljungström A Rydzik 《Acta veterinaria Scandinavica》2004,45(3):149
A pen study was conducted to assess the effect of providing daily copper mineral supplement, or copper wire particle (COWP)
capsules, on established or incoming mixed nematode infections in young sheep. For lambs with established (6 week old) infections,
COWP resulted in 97% and 56% reduction of the adult and early L4 stages of H. contortus, respectively, compared with controls (p < 0.001). Additionally there was a 74% reduction in Teladorsagia circumcincta infections in the COWP lambs compared with controls (p < 0.01). However, no effect was observed when COWP were given at the
commencement of a larval dosing period of 6 weeks. There was no significant effect of copper mineral supplement (given at
the recommended rate to prevent Cu deficiency) on either established, or developing parasite infections. In addition, a field
trial was conducted on a commercial farm to assess the effects of COWP in the management of recurrent H. contortus infections, but lack of parasites during the grazing season prevented an adequate assessment from being made. These results
indicate that there is little, if any, benefit from a parasite control standpoint in recommending copper therapy, specifically
to control parasites in Swedish sheep flocks. 相似文献
28.
As a continuation of studies of the regenerative capacitiesof the scyphistoma of Cassiopea, a series of experiments wasundertaken in which (i) regenerating fragments were culturedin the presence of various antimetabolites and (ii) Feulgenstainednuclei from control animals and regenerating fragments weremeasured by scanning, integrating microspectrophotometry. Theresults of the antimetabolite experiments were complex and variablebut nonetheless suggested that normal regeneration of functionalheads from fragments requires the synthesis of DNA, RNA, andprotein. Regardless of the type of antimetabolite, the mostfrequently observed morphological effect was prolonged or arresteddevelopment. None of the antimetabolites produced characteristicor unique abnormalities, although variation was observed inthe ability of the inhibited fragments to recover from the variousantimetabolites. Microspectrophotometric measurements of Feulgen-stainednuclei from control animals revealed that approximately 25%of the nuclei contained more than the diploid amount of DNAand thus were in either the S or G2 phases of the cell cycle.In regenerating fragments, the frequency of nuclei in this categorydropped progressively to less than 6% by the end of 3 days butreturned nearly to control levels by the end of six days. Thenuclei also became somewhat enlarged and less dense during regeneration. 相似文献
29.
Evolving concepts in plant glycolysis: two centuries of progress 总被引:4,自引:0,他引:4
CURTIS V. GIVAN 《Biological reviews of the Cambridge Philosophical Society》1999,74(3):277-309
Glycolysis, the process responsible for the conversion of monosaccharides to pyruvic acid, is a ubiquitous feature of cellular metabolism and was the first major biochemical pathway to be well characterized. Although the majority of glycolytic enzymes are common to all organisms, the past quarter of a century has revealed that glycolysis in higher plants possesses numerous distinctive features. Research in the nineteenth century established convincingly that plants carry out alcoholic fermentation under anaerobic conditions. In 1878, Wilhelm Pfeffer asserted that a non-oxygen-requiring ‘intramolecular respiration’ was involved in the aerobic respiration of plants. Between 1900 and 1950 it was demonstrated that plants metabolize sugar and starch by a glycolytic pathway broadly similar to that of yeasts and muscle tissue. In 1948, the first purification and characterization of a plant glycolytic enzyme, aldolase, was published by Paul Stumpf. By 1960 the presence of each of the 10 enzymes of glycolysis, presumed at the time to be located in the cytosol, had been confirmed in higher plants. Shortly after 1960 it was shown that the mechanism of glycolytic regulation in plants had features in common with that of animals and yeasts, especially as regards the important role played by the enzyme phosphofructokinase; but important regulatory properties peculiar to plants were soon demonstrated. In the last 30 years, higher-plant glycolysis has been found to exhibit a number of additional characteristics peculiar to plant systems. One conspicuous feature of plant glycolysis, discovered in the 1970s, is the presence of a complete or nearly complete sequence of glycolytic enzymes in plastids, distinct and spatially separated from the glycolytic enzymes located in the cytosol. Plastidic and cytosolic isoenzymes of glycolysis have been shown to differ in their kinetic and regulatory properties, suggesting that the two pathways are independently regulated. Since about 1980 it has become increasingly clear that the cytosolic glycolysis of plants may make use of several enzymes other than the conventional ones found in yeasts, muscle tissue and plant plastids: these enzymes include a pyrophosphate-dependent phosphofructokinase, a non-reversible and nonphosphorylating glyceraldehyde-3-phosphate dehydrogenase, a phosphoenolpyruvate phosphatase (vacuolar location) and a three-enzyme sequence able to produce pyruvate from phosphoenolpyruvate avoiding the pyruvate-kinase step. These non-conventional enzymes may catalyze glycolysis in the plant cytosol especially under conditions of metabolic stress. Experiments on transgenic plants possessing significantly elevated or reduced (reduced to virtually nil in some cases) levels of glycolytic enzymes are currently playing an important part in improving our understanding of the regulation of plant glycolysis; such experiments illustrate an impressive degree of flexibility in the pathway's operation. Plant cells are able to make use of enzymes bypassing or substituting for several of the conventional enzymic steps in the glycolytic pathway; the extent and conditions under which these bypasses operate are the subject of current research. The duplication of the glycolytic pathway in plants and the flexible nature of the pathway have possibly evolved in relation to the crucial biosynthetic role played by plant glycolysis beyond its function in energy generation; both functions must proceed if a plant is to survive under varying and often stressful environmental or nutritional conditions. 相似文献
30.
Eduardo N Taboada Joanne M MacKinnon Christian C Luebbert Victor PJ Gannon John HE Nash Kris Rahn 《BMC evolutionary biology》2008,8(1):229