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101.
拐芹根化学成分研究Ⅱ 总被引:3,自引:0,他引:3
从伞型科当归属植物拐芹(Angelica polymorpha Maxim)的根及根茎中又分得4个结晶性化合物。经物理常数测定、光谱分析,分别鉴定为欧前胡素Ⅰ,异氧化前胡内酯Ⅱ,Pabulenol Ⅲ,Phellopterin Ⅳ。 相似文献
102.
Maud E. Quist 《Plant and Soil》1995,176(2):297-305
Herbs and grasses may episodically be exposed to elevated concentrations of potentially toxic elements as H+ and Al3+ due to considerable temporal variability in the chemical composition of soil solutions in the uppermost layer of the soil profile. Greenhouse experiments were performed to test the effect of episodes of different length (1 and 2 weeks) and concentrations of H+ and Al3+ (pH 3.8, 4.0, 4.2 and 4.5; 0, 20 and 70 M Al) on root and shoot growth, designed to elucidiate the reversibility of growth inhibition. Three forest floor species were studied-Galium odoratum and Lamium galeobdolon, having similar pH distribution ranges in the field and Poa nemoralis which also occurs at slightly lower pH. The plants were grown for 5 weeks (episode and recovering time) in a synthetic soil solution in a flowing solution system without recirculation. The species reacted in three different ways. Galium odoratum was the most sensitive species and seemed to be irreversibly damaged (ceased growth) by 2 week episodes of pH4.0 and Al20 M at pH4.2. Lamium galeobdolon was about equally sensitive during the episodes but it had a much greater ability to recover. Poa nemoralis was rather insensitive to the episode treatments tested. It is concluded that episodes of elevated H+ and Al3+ concentrations may be decisive for plant performance. It is therefore important to consider the extreme environmental conditions which plants may be exposed to in the field, in addition to long-term averages of e.g. soil solution concentration of potentially toxic elements, when studying species distribution and performance in relation to soil chemical properties. 相似文献
103.
Mitochondrial DNA (mtDNA) sequences that include (a) a part of the
cytochrome b gene, (b) two tRNA genes, and (c) a part of the noncoding
D-loop region of 31 Anguilla japonica (Japanese eel) and 1 A. marmorata
collected from Taiwan, Japan, and mainland China were determined to
evaluate the population structure of Japanese eel. Among 30 genotypes
identified from the 31 Japanese eel mtDNAs sequenced, there are 58 variable
sites, predominantly clustered at the D-loop region. The phylogenetic tree
constructed by the unweighted pair-group method with arithmetic mean shows
neither significant genealogical branches nor geographic clusters.
Furthermore, the sequence-statistics test reveals little, if any,
significant genetic differentiation. These results indicate that the 31
Japanese eels might come from a single population. Analysis of sequence
variation in mtDNA by using the relationship between the number of
segregating sites and the average number of nucleotide differences under
the neutral mutation hypothesis reveals that neutral mutation acts as a
major factor influencing the evolutionary divergence of the Japanese eel
mitochondrial genome sequenced, especially in the noncoding region.
相似文献
104.
Rocke TE Thomas NJ Meteyer CU Quist CF Fischer JR Augspurger T Ward SE 《Journal of wildlife diseases》2005,41(1):163-170
Attempts were made to reproduce avian vacuolar myelinopathy (AVM) in a number of test animals in order to determine the source of the causative agent for birds and to find a suitable animal model for future studies. Submerged vegetation, plankton, invertebrates, forage fish, and sediments were collected from three lakes with ongoing outbreaks of AVM and fed to American coots (Fulica americana), mallard ducks and ducklings (Anas platyrhynchos), quail (Coturnix japonica), and laboratory mice either via gavage or ad libitum. Tissues from AVM-affected coots with brain lesions were fed to ducklings, kestrels (Falco sparverius), and American crows (Corvus brachyrhynchos). Two mallards that ingested one sample of Hydrilla verticillata along with any biotic or abiotic material associated with its external surface developed brain lesions consistent with AVM, although neither of the ducks had clinical signs of disease. Ingestion of numerous other samples of Hydrilla from the AVM affected lakes and a lake with no prior history of AVM, other materials (sediments, algae, fish, invertebrates, and water from affected lakes), or tissues from AVM-affected birds did not produce either clinical signs or brain lesions in any of the other test animals in our studies. These results suggest that waterbirds are most likely exposed to the causative agent of AVM while feeding on aquatic vegetation, but we do not believe the vegetation itself is the agent. We hypothesize that the causative agent of AVM might either be accumulated by aquatic vegetation, such as Hydrilla, or associated with biotic or abiotic material on its external surfaces. In support of that hypothesis, two coots that ingested Hydrilla sampled from a lake with an ongoing AVM outbreak in wild birds developed neurologic signs within 9 days (ataxia, limb weakness, and incoordination), and one of two coots that ingested Hydrilla collected from the same site 13 days later became sick and died within 38 days. None of these three sick coots had definitive brain lesions consistent with AVM by light microscopy, but they had no gross or histologic lesions in other tissues. It is unclear if these birds died of AVM. Perhaps they did not ingest a dose sufficient to produce brain lesions or the lesions were ultrastructural. Alternatively, it is possible that a separate neurotoxic agent is responsible for the morbidity and mortality observed in these coots. 相似文献
105.
Quist CF Nettles VF Manning EJ Hall DG Gaydos JK Wilmers TJ Lopez RR 《Journal of wildlife diseases》2002,38(4):729-737
Paratuberculosis was diagnosed in an endangered Key deer (Odocoileus virginianus clavium) in November 1996. Between 10 April 1997 and 28 September 2000, the Key deer population was monitored for infection with Mycobacterium avium subsp. paratuberculosis by necropsy of available carcasses (n = 170), fecal cultures, and serology. One additional clinically affected Key deer was discovered in July 1998, and M. avium subsp. paratuberculosis was cultured from the feces of one live, asymptomatic deer. The results of this study provided sufficient evidence to consider the Key deer herd infected with M. avium subsp. paratuberculosis at very low prevalence. 相似文献
106.
Mateus F Santana José CF Silva Eduardo SG Mizubuti Elza F Araújo Bradford J Condon B Gillian Turgeon Marisa V Queiroz 《BMC genomics》2014,15(1)
Background
Cochliobolus heterostrophus is a dothideomycete that causes Southern Corn Leaf Blight disease. There are two races, race O and race T that differ by the absence (race O) and presence (race T) of ~ 1.2-Mb of DNA encoding genes responsible for the production of T-toxin, which makes race T much more virulent than race O. The presence of repetitive elements in fungal genomes is considered to be an important source of genetic variability between different species.Results
A detailed analysis of class I and II TEs identified in the near complete genome sequence of race O was performed. In total in race O, 12 new families of transposons were identified. In silico evidence of recent activity was found for many of the transposons and analyses of expressed sequence tags (ESTs) demonstrated that these elements were actively transcribed. Various potentially active TEs were found near coding regions and may modify the expression and structure of these genes by acting as ectopic recombination sites. Transposons were found on scaffolds carrying polyketide synthase encoding genes, responsible for production of T-toxin in race T. Strong evidence of ectopic recombination was found, demonstrating that TEs can play an important role in the modulation of genome architecture of this species. The Repeat Induced Point mutation (RIP) silencing mechanism was shown to have high specificity in C. heterostrophus, acting only on transposons near coding regions.Conclusions
New families of transposons were identified. In C. heterostrophus, the RIP silencing mechanism is efficient and selective. The co-localization of effector genes and TEs, therefore, exposes those genes to high rates of point mutations. This may accelerate the rate of evolution of these genes, providing a potential advantage for the host. Additionally, it was shown that ectopic recombination promoted by TEs appears to be the major event in the genome reorganization of this species and that a large number of elements are still potentially active. So, this study provides information about the potential impact of TEs on the evolution of C. heterostrophus.Electronic supplementary material
The online version of this article (doi:10.1186/1471-2164-15-536) contains supplementary material, which is available to authorized users. 相似文献107.
Mattia CF Prosperi Susana Marinho Angela Simpson Adnan Custovic Iain E Buchan 《BMC medical genomics》2014,7(Z1):S7
Background
There is increasing recognition that asthma and eczema are heterogeneous diseases. We investigated the predictive ability of a spectrum of machine learning methods to disambiguate clinical sub-groups of asthma, wheeze and eczema, using a large heterogeneous set of attributes in an unselected population. The aim was to identify to what extent such heterogeneous information can be combined to reveal specific clinical manifestations.Methods
The study population comprised a cross-sectional sample of adults, and included representatives of the general population enriched by subjects with asthma. Linear and non-linear machine learning methods, from logistic regression to random forests, were fit on a large attribute set including demographic, clinical and laboratory features, genetic profiles and environmental exposures. Outcome of interest were asthma, wheeze and eczema encoded by different operational definitions. Model validation was performed via bootstrapping.Results
The study population included 554 adults, 42% male, 38% previous or current smokers. Proportion of asthma, wheeze, and eczema diagnoses was 16.7%, 12.3%, and 21.7%, respectively. Models were fit on 223 non-genetic variables plus 215 single nucleotide polymorphisms. In general, non-linear models achieved higher sensitivity and specificity than other methods, especially for asthma and wheeze, less for eczema, with areas under receiver operating characteristic curve of 84%, 76% and 64%, respectively. Our findings confirm that allergen sensitisation and lung function characterise asthma better in combination than separately. The predictive ability of genetic markers alone is limited. For eczema, new predictors such as bio-impedance were discovered.Conclusions
More usefully-complex modelling is the key to a better understanding of disease mechanisms and personalised healthcare: further advances are likely with the incorporation of more factors/attributes and longitudinal measures.108.
Casper W. Quist Mariëtte T. W. Vervoort Hanny Van Megen Gerrit Gort Jaap Bakker Wim H. Van der Putten Johannes Helder 《Oikos》2014,123(7):837-845
Apart from relatively well‐studied aboveground effects, invasive plant species will also impact the soil food web. So far, most research has been focusing on primary decomposers, while studies on effects at higher trophic levels are relatively scarce. Giant goldenrod Solidago gigantea, native to North America, is a widespread and common invasive species in most European countries. We investigated its impact on plant communities and on multiple trophic levels of the soil food web in two contrasting habitats: riparian zones and semi‐natural grasslands. In 30 pairs of invaded and uninvaded plots, floristic composition, pH, fungal biomass and the densities of 11 nematode taxa were determined by using a quantitative PCR‐based method. In the two habitats, the invader outcompeted both rare and dominant plant species. Belowground, S. gigantea invasion reduced pH, increased overall fungal biomass as well as the density of a single lineage of fungivorous nematodes, the family Aphelenchoididae. The densities of two other, phylogenetically distinct lineages of fungivorous nematodes, Aphelenchidae and Diphtherophoridae, were unaffected by the local increase in fungal biomass. Apparently this plant species induces a local asymmetric boost of the fungal community, and only Aphelenchoididae were able to benefit from this invader‐induced change. The alternative explanation – the results are explained by a subtle, S. gigantea‐induced 0.1–0.2 units decrease of pH – seems unlikely, as pH optima for nematode taxa are relatively broad. Thus, apart from readily observable aboveground effects, the invasive plant species S. gigantea affects fungal biomass as well as a specific part of the fungivorous nematode community in a soil type‐independent manner. 相似文献
109.
By J. D. Koch M. C. Quist K. A. Hansen G. A. Jones 《Zeitschrift fur angewandte Ichthyologie》2009,25(5):545-550
Bowfin Amia calva are a common species throughout the Mississippi River basin. Although they are generally regarded as a 'rough' fish by management agencies and anglers, commercial harvest for their roe has increased in the upper Mississippi River (UMR) basin. Unfortunately, bowfin population dynamics have not received extensive study, resulting in a lack of information that can be used to guide management efforts, particularly in the UMR. The purpose of this study was to investigate the age structure, growth, and reproductive ecology (e.g. age at maturity, fecundity) of bowfin in Pools 11 and 13 of the UMR during the spring of 2007. 118 bowfin from Pool 11 and 138 bowfin from Pool 13 were sampled using modified fyke nets and electrofishing. Size structure, age structure, and growth were similar and sex ratios were near 1:1 in both pools. Female bowfin matured at age 3 and had gonadosomatic index (GSI) values around 9; male bowfin matured at age 2 and had GSI values near 1. Total annual mortality of age-4 and older fish was around 35% for both populations. In both pools, rates of total annual mortality of males were approximately 10% higher than those of females. Growth overfishing occurred in a simulated population with a 500-mm minimum length limit. Recruitment overfishing occurred with 500-mm, 559-mm, and 584-mm limits at moderate to high levels of exploitation; a 635-mm minimum prevented recruitment overfishing at all levels of exploitation. 相似文献
110.
The differential impact of a native and a non‐native ragwort species (Senecioneae) on the first and second trophic level of the rhizosphere food web
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Paula Harkes Ava Verhoeven Mark G. Sterken L. Basten Snoek Sven J. J. van den Elsen Paul J. W. Mooijman Casper W. Quist Mariëtte T. W. Vervoort Johannes Helder 《Oikos》2017,126(12):1790-1803
Whereas the impact of exotic plant species on above‐ground biota is relatively well‐documented, far less is known about the effects of non‐indigenous plants on the first and second trophic level of the rhizosphere food web. Here, rhizosphere communities of the invasive narrow‐leaved ragwort Senecio inaequidens and the native tansy ragwort Jacobaea vulgaris, co‐occurring in three semi‐natural habitats are compared. For both species, two life stages were taken into consideration. Quantitative PCR assays for the analyses of bacterial and fungal communities at a high taxonomic level were optimized, and it was investigated whether changes in the primary decomposer community were translated in alterations in bacterivorous and fungivorous nematode communities. In contrast to J. vulgaris, small but significant reductions were observed for Actinobacteria and Bacteroidetes (both p < 0.05) in case of the invasive S. inaequidens. More pronounced changes were detected for the overall nematode community density, and, more specifically, for the bacterivorous genus Anaplectus and the family Monhysteridae (both p < 0.05), as well as the necromenic Pristionchus (p < 0.001). At high taxonomic level, no differences were observed in fungal rhizosphere communities between native and non‐native ragwort species. The impact of plant developmental stages on rhizosphere biota was prominent. The overall bacterial and fungal biomasses, as well as a remarkably consistent set of constituents (Actinobacteria, α‐ and β‐Proteobacteria and Bacteroidetes) were negatively affected by plant stage for both ragwort species. Although later developmental stages of plants generally coincided with lower levels for individual nematode taxa, densities of the fungivorous genera Diphtherophora and Tylolaimophorus remain unaltered. Hence, even at a high taxonomic level, differential effects of native and non‐native ragwort could be pinpointed. However, plant developmental stage has a more prominent impact and this impact was similar in nature for both native and non‐native ragwort species. 相似文献