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排序方式: 共有5755条查询结果,搜索用时 31 毫秒
1.
Michael G. G. Foreman Ming Guo Kyle A. Garver Dario Stucchi Peter Chandler Di Wan John Morrison Darren Tuele 《PloS one》2015,10(6)
Finite volume ocean circulation and particle tracking models are used to simulate water-borne transmission of infectious hematopoietic necrosis virus (IHNV) among Atlantic salmon (Salmo salar) farms in the Discovery Islands region of British Columbia, Canada. Historical simulations for April and July 2010 are carried out to demonstrate the seasonal impact of river discharge, wind, ultra-violet (UV) radiation, and heat flux conditions on near-surface currents, viral dispersion and survival. Numerical particles released from infected farm fish in accordance with IHNV shedding rates estimated through laboratory experiments are dispersed by model oceanic flows. Viral particles are inactivated by ambient UV radiation levels and by the natural microbial community at rates derived through laboratory studies. Viral concentration maps showing temporal and spatial changes are produced and combined with lab-determined minimum infectious dosages to estimate the infective connectivity among farms. Results demonstrate that neighbouring naïve farms can become exposed to IHNV via water-borne transport from an IHNV diseased farm, with a higher risk in April than July, and that many events in the sequence of farm outbreaks in 2001-2002 are consistent with higher risks in our farm connectivity matrix. Applications to other diseases, transfers between farmed and wild fish, and the effect of vaccinations are also discussed. 相似文献
2.
Shraddha Nayak Md. Abdul H. Khan Tina C. Wan Hong Pei Joel Linden Melinda R. Dwinell Aron M. Geurts John D. Imig John A. Auchampach 《Purinergic signalling》2015,11(4):519-531
The A2B adenosine receptor (AR) has emerged as a unique member of the AR family with contrasting roles during acute and chronic disease states. We utilized zinc-finger nuclease technology to create A2BAR gene (Adora2b)-disrupted rats on the Dahl salt-sensitive (SS) genetic background. This strategy yielded a rat strain (SS-Adora2b mutant rats) with a 162-base pair in-frame deletion of Adora2b that included the start codon. Disruption of A2BAR function in SS-Adora2b mutant rats was confirmed by loss of agonist (BAY 60-6583 or NECA)-induced cAMP accumulation and loss of interleukin-6 release from isolated fibroblasts. In addition, BAY 60-6583 produced a dose-dependent increase in glucose mobilization that was absent in SS-Adora2b mutants. Upon initial characterization, SS-Adora2b mutant rats were found to exhibit increased body weight, a transient delay in glucose clearance, and reduced proinflammatory cytokine production following challenge with lipopolysaccharide (LPS). In addition, blood pressure was elevated to a greater extent (∼15–20 mmHg) in SS-Adora2b mutants as they aged from 7 to 21 weeks. In contrast, hypertension augmented by Ang II infusion was attenuated in SS-Adora2b mutant rats. Despite differences in blood pressure, indices of renal and cardiac injury were similar in SS-Adora2b mutants during Ang II-augmented hypertension. We have successfully created and validated a new animal model that will be valuable for investigating the biology of the A2BAR. Our data indicate varying roles for A2BAR signaling in regulating blood pressure in SS rats, playing both anti- and prohypertensive roles depending on the pathogenic mechanisms that contribute to blood pressure elevation. 相似文献
3.
免疫细胞浸润对癌症的诊断与预后有着重要意义。文中收集TCGA数据库已收录的非小细胞肺癌肿瘤与正常组织基因表达数据,利用CIBERSORT工具得到22种免疫细胞占比来评估免疫细胞浸润情况。以22种免疫细胞占比为特征,用机器学习方法构建了非小细胞肺癌肿瘤与正常组织的分类模型,其中随机森林方法构建的模型分类效果AUC=0.987、敏感性0.98及特异性0.84。并且用随机森林方法构建的肺腺癌和肺鳞癌肿瘤组织分类模型效果AUC=0.827、敏感性0.75及特异性0.77。用LASSO回归筛选22种免疫细胞特征,保留8种强相关特征组成的免疫细胞评分结合临床特征构建了非小细胞肺癌预后模型。经评估及验证,预后模型C-index=0.71并且3年和5年的校准曲线拟合良好,可以对预后风险度进行准确预测。本研究基于免疫细胞浸润所构建的分类模型与预后模型,旨在对非小细胞肺癌的诊断与预后研究提供新的策略。 相似文献
4.
Does hydraulic lift exist in shallow-rooted species? A quantitative examination with a half-shrub Gutierrezia sarothrae 总被引:1,自引:0,他引:1
Hydraulic lift occurs in some deep-rooted shrub and herbaceous species. In this process, water taken up by deep roots from
the moist subsoil is delivered to the drier topsoil where it is later reabsorbed by shallow roots. However, little is known
about the existence of hydraulic lift in shallow-rooted xeric species. The objectives of this study were 1) to ascertain whether
hydraulic lift exists in Gutierrezia sarothrae (broom snakeweed), a widespread North American desert species with a shallow root system, grown in pot and field conditions
and 2) if it does, how much water can be transferred from the subsoil to the 30 cm topsoil during the night. Snakeweed seedlings
were transplanted in buried pots allowing the deeper roots to grow into the subsoil 30 cm below the surface. Soil water content
inside and outside of the pot was measured seasonally and diurnally with time domain reflectometry technique (TDR). An increase
in water content was detected in the pot after the plant was covered for 3 h by an opaque plastic bag during the day, suggesting
hydraulic lift from deeper depths and exudation of water into the drier topsoil. Root exudation was also observed on native
range sites dominated by snakeweed. Water efflux in the pot was 271 g per plant per night. which was equivalent to 15.3% of
the extrapolated, porometer-derived whole-plant daily transpiration. Hydraulic lift observed in Gutierrezia improved water uptake during the day when evaporative demand is high and less water is available in the topsoil. We concluded
that hydraulic lift might help snakeweed to alleviate the effect of water stress. 相似文献
5.
6.
Food availability is important to the dynamics of animal social organizations or populations. However, the role of winter
food availability in animal population dynamics is still controversial. We carried out an experimental study to test Lack’s
hypothesis that reduced food in winter limits survival and spring numbers of breeding individuals of social groups, using
the Mongolian gerbil (Meriones unguiculatus) as model species. We established 24 gerbil social groups in 24, 10 × 10 m, pens in September 2008. We provided wheat seeds
as supplemental food in 12 enclosures from September 2008 to March 2009; the other 12 enclosures, not provided with supplemental
food, served as controls. We live-trapped gerbils at a 2-week interval from September to April. Supplemental food during winter
increased biweekly survival by 10% relative to that in control groups. Only four control social groups survived to the end
of our study whereas all 12 food-supplemented social groups survived through our study period. Supplemental food also increased
cumulative numbers of recruits and group sizes of gerbils. We conclude that winter food availability limits winter survival
and spring social groups or population sizes of Mongolian gerbils. 相似文献
7.
An interspecific somatic hybrid between Actinidia chinensis and Actinidia kolomikta and its chilling tolerance 总被引:2,自引:0,他引:2
Protoplasts isolated from cotyledon-derived callus of Actinidia chinensisPlanch. var. chinensis (2N=2x=58) were fused with mesophyll protoplasts of Actiniadia kolomikta(Maxim. et Rupr.) Maxim (2N=2x=58) using a PEG method. Plantlets were regenerated from the fusion product clone 11. RAPD analyses, chromosome numbers of root tip cells and fluorescence peak position of leaf nuclei confirmed that clone 11 was an interspecific somatic hybrid (2N=4x=116) between A. chinensis and A. kolomikta. The chilling tolerance of the somatic hybrid was tested with in vitro leaves at low temperatures. Based on data of leaf thickness, electroconductivity, proline levels, malondialdehyde content and activity of superoxide dismutase, dendrogram cluster analysis suggested that the interspecific somatic hybrid was similar to A. kolomikta, and might have a higher capacity of cold resistance than A. chinensis. 相似文献
8.
Spartina alterniflora is a perennial salt marsh grass native to the Atlantic and Gulf Coasts of North America. Recognized for its effects of diminishing strong tide even storms and accelerating sediment deposition, S. alterniflora was introduced into China in 1979. Now the artificial vegetation of Spartina has expanded to around 50 000 h m2 along the east coast of China due to its strong capability of propagating by seeds and rhizome fragments. Although it was listed among 16 harmful exotic species in China 3 years ago, we need to evaluate its positive and negative effects in the coastal region of China objectively. This paper reviews some major positive effects of S. alterniflora in China, e.g. being a dominant primary producer, buffering against tides, accelerating accretion and reclamation, absorbing nutrients and digesting pollutants, as well as some major negative effects, e.g. occupying the niche of local species, altering the mudflat habitat, changing and even diminishing biodiversity, and damaging the aquiculture in the tidal land. In addition, its biomaterial uses and biological substitution as a means of ecological regulation is also discussed. 相似文献
9.
The effects of irrigation and fertiliser regimes on N leaching from the production of couch grass (Cynodon dactylon L.) sod, on a free-draining sandy soil, were evaluated in a 22-month field study. The experimental design used a randomised-block,
split-plot design with three replicates. Main plots consisted of two irrigation treatments: 70 and 140% daily replacement
of pan evaporation; four subplot fertiliser types (water-soluble (predominately NH4NO3), control-release, pelletised poultry manure and pelletised biosolids); and three N application rates (100, 200 and 300 kg
N ha−1 per crop). Nitrogen leaching was assessed by measuring the leachate volumes and concentrations of N species leached from
soil lysimeters (250 mm in diameter by 950 mm in length) installed in 10 m2 turfgrass plots. Nitrogen leaching ranged from 33 to 167 kg N ha−1 over 22 months, depending upon the irrigation and fertiliser treatment. Irrigation treatment affected N leaching more than
fertiliser treatment, and increasing the irrigation from 70 to 140% replacement of daily pan evaporation increased N leaching
for all fertiliser types, and by up to four times. Forty six to 76% of losses occurred from the high irrigation treatments
during the first 16 weeks after the turfgrass was planted as rhizomes. By contrast, N leaching did not appear to increase
following harvest of sod. At the high irrigation treatment, N leaching was greater for the pelletised biosolids than the control-release;
while at the low irrigation treatment, N leaching did not vary between fertiliser types. A significant proportion of the N
leached was in the organic form. Therefore, we recommend total N and mineral N be measured when assessing N leaching from
turfgrass. Nitrogen leaching from turfgrass production is low from all fertiliser types when the irrigation matches turfgrass
water use and N is applied at a rate and frequency that approximates turfgrass requirements.
Section Editor: P. J. Randall 相似文献
10.
beta-D-Mannosidase (EC 3.2.1.25), a useful tool for the structural studies of heterosaccharide chains, has been isolated in a highly purified form from the fruiting bodies of the mushroom Polyporus sulfureus. This mushroom is unique among reported sources of this enzyme in that it has the advantage of being almost free of alpha-mannosidase activity. The purification procedure involves ammonium sulfate fractionation followed by Sephadex G-100 filtration and chromatography on columns of DEAE-cellulose and hydroxylapatite. The final enzyme preparation gives essentially a single band on disc gel electrophoresis. The purified enzyme liberates the beta-D-mannopyranosyl unit from various natural substrates such as the core glycopeptide, Man(GlcNAc)2-Asn isolated from ovalbumin, from Taka-amylase A, and from human alpha1-acid glycoprotein. It also hydrolyzes (Man)2-GlcNAc from the urine of an alpha-mannosidosis patient, 1,4-D-mannobiose and mannotriose isolated from ivory nut mannan, 4-O-beta-D-mannopyranosyl-L-rhamnose, 6-O-beta-D-mannopyranosyl-D-galactose and 4-O-beta-D-mannopyranosyl-N-acetylglucosamine. The molecular weight of this enzyme is estimated to be about 64,000 by gel filtration. For p-nitrophenyl-beta-D-mannopyranoside, the pH optimum is between 2.4 and 3.4 and the Km is 1.6 mM. 相似文献