Policy. OPV cessation--the final step to a "polio-free" world     

Aylward RB  Sutter RW  Heymann DL 《Science (New York, N.Y.)》2005,310(5748):625-626

The 20-year, U.S. $4 billion-dollar international effort to eradicate wild polioviruses now includes monovalent oral poliovirus type 1 vaccine (mOPV1), which was first given to 40 million children in India in April 2005. As this vaccine is being introduced to eliminate some of the last poliovirus reservoirs, the Global Polio Eradication Initiative is planning for the eventual synchronized worldwide cessation of the routine use of all oral poliovirus vaccines (OPVs) because of their capacity to cause, rarely, outbreaks of paralytic poliomyelitis. This Policy Forum reviews the feasibility and implications of eventually stopping the use of live polio vaccines.  相似文献   

Amyloid fibrils of the HET-s(218-289) prion form a beta solenoid with a triangular hydrophobic core     

Wasmer C  Lange A  Van Melckebeke H  Siemer AB  Riek R  Meier BH 《Science (New York, N.Y.)》2008,319(5869):1523-1526

Prion and nonprion forms of proteins are believed to differ solely in their three-dimensional structure, which is therefore of paramount importance for the prion function. However, no atomic-resolution structure of the fibrillar state that is likely infectious has been reported to date. We present a structural model based on solid-state nuclear magnetic resonance restraints for amyloid fibrils from the prion-forming domain (residues 218 to 289) of the HET-s protein from the filamentous fungus Podospora anserina. On the basis of 134 intra- and intermolecular experimental distance restraints, we find that HET-s(218-289) forms a left-handed beta solenoid, with each molecule forming two helical windings, a compact hydrophobic core, at least 23 hydrogen bonds, three salt bridges, and two asparagine ladders. The structure is likely to have broad implications for understanding the infectious amyloid state.  相似文献   

Structures of glycoprotein Ibalpha and its complex with von Willebrand factor A1 domain     

Huizinga EG  Tsuji S  Romijn RA  Schiphorst ME  de Groot PG  Sixma JJ  Gros P 《Science (New York, N.Y.)》2002,297(5584):1176-1179

Transient interactions of platelet-receptor glycoprotein Ibalpha (GpIbalpha) and the plasma protein von Willebrand factor (VWF) reduce platelet velocity at sites of vascular damage and play a role in haemostasis and thrombosis. Here we present structures of the GpIbalpha amino-terminal domain and its complex with the VWF domain A1. In the complex, GpIbalpha wraps around one side of A1, providing two contact areas bridged by an area of solvated charge interaction. The structures explain the effects of gain-of-function mutations related to bleeding disorders and provide a model for shear-induced activation. These detailed insights into the initial interactions in platelet adhesion are relevant to the development of antithrombotic drugs.  相似文献   

Brassica sect.Brassica (Brassicaceae)     

Roland von Bothmer  Mats Gustafsson  Sven Snogerup 《Genetic Resources and Crop Evolution》1995,42(2):165-178

Summary An extensive crossing program including 10 wild taxa and 23 accessions representing 6 major cultivated forms and landraces of theBrassica oleracea group was carried out. Data for crossability, germination, viability, fertility inF ₁ andF ₂ were studied as well as the meiotic chromosomal pairing inF ₁ hybrids in some combinations. The fertility of hybrids between all cultivated forms and wild populations ofB. oleracea was high and it was concluded that all, including the Chinese endemicalboglabra form, belong to the same biological species. Among the other species,B. macrocarpa, B. montana, andB. rupestris had the lowest andB. cretica the highest fertility values in crosses with cultivated forms. The crossing data do not give any further information as to the genetic differentiation ofB. oleracea during the course of domestication. Introgression between wild and cultivated forms has probably occurred frequently. All members of theB. oleracea cytodeme belong to the primary and secondary gene pools of the 18 chromosomic crops and are as such of great importance for breeding purposes.  相似文献   

Zur Parametrisierung der Stickstoff-Mineralisierung in einem Ackerboden unter Feldbedingungen     

Roland Lochmann  Rienk R. Der Van Ploeg  Bernd Huwe 《植物养料与土壤学杂志》1989,152(3):319-324

A functional relationship for the nitrogen mineralization of an arable soil under field conditions In order to characterize the nitrogen mineralization of a poorly drained, loess-derived field soil (Aeric Fragiaqualf, loamy, mesic) a laboratory incubation experiment was carried out. The measured mineralization rate was expressed as a function of soil temperature and soil water content. At the same time, a field incubation experiment with buried soil samples (so-called Runge samples) was conducted. It was found that the laboratory incubation method overestimated the mineralization rate as compared with the field method. Accordingly, the laboratory data were adjusted. Additionally, it was found that management practices (fertilizer application, harvest, soil cultivation) influenced the course and the extent of the nitrogen mineralization.  相似文献   

Two-dimensional simulation of airflow and carbon dioxide transport over a forested mountain: Part I: Interactions between thermally-forced circulations   总被引：2，自引：0，他引：2  

Haizhen Sun  Terry L. Clark  Roland B. Stull  T. Andrew Black 《Agricultural and Forest Meteorology》2006,140(1-4):338

Local-scale wind regimes over an idealized two-dimensional (2D) mountain having similar horizontal and vertical scales as Vancouver Island were investigated using a high-resolution mesoscale model. The model-generated flow outputs were then used as ersatz data to assess the impact of limiting assumptions in the eddy-covariance (EC) method as well as the effectiveness of tower flux data time-filtering for the main tower site of the Fluxnet-Canada British Columbia flux station. In this paper, we describe the simulated mesoscale and local-scale flow regimes, and in Part II we describe their use in assessing tower-data analyses of CO₂ fluxes.The numerical model was enhanced to include parameterizations for: tree drag, radiation effects of forest canopies on the surface energy budget, and soil heat conduction. Simulations were performed both over an idealized bare hill and over a forested hill. The simulated flow involved interactions between the land/sea breeze, convective thermals, and mountain circulations under fair-weather conditions.The resulting simulated winds over the forested slope were much weaker than those over a bare slope. The nocturnal drainage flow over the forested slope was separated into sub-canopy and above-canopy regimes due to the temperature inversion at treetop. The strongest downslope flows occurred above the canopy with a minimum velocity occurring in the upper canopy where canopy drag is the strongest. The overturning of large convective eddies during daytime resulted in intermittent downslope flows under the canopy during the day. Wind regimes had a rapid shift from upslope to downslope flow above the canopy just after sunset. Further testing will be made using 3D simulations with higher resolution.  相似文献   

Recalcitrant soil organic materials mineralize more efficiently at higher temperatures     

Roland Bol  Thomas Bolger  Raymond Cully  Declan Little 《植物养料与土壤学杂志》2003,166(3):300-307

As concentrations of atmospheric CO₂ increase, it is important to know whether this may result in feedbacks that could modify the rate of increase of CO₂ in the atmosphere. Soil organic matter (SOM) represents one of the largest pools of C and mineralization rates are known to be temperature dependent. In this study, we investigated whether different OM fractions present in a forest soil (F/A1 horizon) would respond in a similar manner to elevated temperatures. We examined the trends in isotopic content (¹²C, ¹³C, and ¹⁴C) of soil respired CO₂ at various temperatures (10, 20, and 35 ⁰C) over a two year period in the laboratory. We also examined the total C, total N, and C : N ratio in the remaining soil and isolated humic fractions, and the distribution of the individual amino acids in the soil after 5 years of laboratory incubation at the various temperatures. We found that the rate at which C mineralization increases with temperature was occasionally greater than predicted by most models, more C from recalcitrant OM pools being mineralized at the higher temperature. This confirmed that the relationship between soil organic matter decomposition and temperature was complex and that the different pools of organic matter did respond in differing ways to elevated temperatures.  相似文献   

Germplasm characterization of Sesbania accessions based on isozyme analyses     

Elizabeth Ann Veasey  Roland Vencovsky  Paulo Sodero Martins  Gerhard Bandel 《Genetic Resources and Crop Evolution》2002,49(5):449-462

Twenty-two accessions belonging to seven species of Sesbania Scop. (S. emerus, S. exasperata, S. grandiflora, S. rostrata, S. sesban, S. tetrapteraand S. virgata), were evaluated in order to characterize the isozyme electrophoretic patterns and to estimate their genetic variability and outcrossing rates. Eight isozyme systems were used: acid phosphatase (ACP), isocitrate dehydrogenase (IDH), phosphoglucomutase (PGM), malate dehydrogenase (MDH), phosphoglucoisomerase (PGI), glutamate oxaloacetate transaminase (GOT), peroxidase (PRX) and catalase (CAT), with two gel/electrode buffers and distilled water as the extraction buffer. Cotyledons were chosen for enzyme extraction. The accessions were compared considering the presence/absence of bands for each system. A dendrogram was obtained using the Jaccard similarity index and the UPGMA clustering method, classifying the accessions into eight groups, evidencing both inter- and intraspecific variability. Annual species were classified in one major group separate from the perennials (S. grandiflora, S. sesban, S. virgata), which were allocated into two other main groups. S. virgata accessions (subgenus Daubentonia) were clearly separated from the other species. Isozyme banding patterns for the accessions are presented for each system. A high incidence of intraspecific monomorphism was observed. Interpretation in terms of loci and alleles was made for S. sesbanand S. virgataaccessions, which presented polymorphism for the systems PGI, GOT (S. sesban) and MDH (S. virgata). The average expected heterozygosity estimates varied from 0.0 to 0.231 for S. sesban and 0.0 to 0.20 for S. virgata. A mean number of 2.0 alleles per locus was observed for both species. Population multilocus outcrossing rate (t _m) of 0.62 was estimated for S. sesban, indicating a partial allogamy mode of reproduction. Individual families presented multilocus rates varying from 0.00 to 1.00, indicating both self-pollination and cross-pollination.  相似文献   

Assessment of the impact of climate change on the latency period of leaf rust on triticale in Poland     

Andrzej Wójtowicz  Marek Wójtowicz  Roland Sigvald  Bartosz Czernecki  Henryk Ratajkiewicz  Agnieszka Łacka 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2020,70(3):195-207

ABSTRACT

Disease development in plants is strongly dependent on weather conditions, with temperature playing a particularly significant role by influencing latency period duration. Using two models describing the relationship between latency period and temperature, we performed simulations aimed at predicting changes in the latency period of leaf rust (Puccina recondita f. sp. tritici) on triticale in response to expected climate change. The simulations were based on meteorological data recorded in the period 1986–2005 at locations representing 16 provinces in Poland and based on values obtained after transformation of the observed data to reflect temperature changes under four scenarios (RCP2.6, RCP4.5, RCP6.0 and RCP8.5) according to the giss_e2_r climate model. In all scenarios, the results for the two triticale cultivars studied, Witon (vulnerable to P. recondita) and Gniewko (less susceptible), showed a threat of faster development (shorter leaf rust latency period) on triticale triggered by climate change in south-east and south-central Poland than in other regions. The results also showed an increased probability of future regional diversification of leaf rust latency period duration on vulnerable triticale cultivars, opportunities for earlier start of leaf rust epidemics on triticale in Poland and an increase in ?nal disease severity in comparison with 1986–2005.  相似文献   

Quantitative analysis of anti-inflammatory and radical scavenging triterpenoid esters in evening primrose oil     

Knorr R  Hamburger M 《Journal of agricultural and food chemistry》2004,52(11):3319-3324

Cold pressed, nonraffinated evening primrose oil (EPO) was recently found to contain lipophilic triterpenoidal esters with radical scavenging and anti-inflammatory properties. A simple and robust method for the quantitative analysis of these 3-O-trans-caffeoyl derivatives of betulinic, morolic, and oleanolic acid was developed and validated. Separation was achieved by normal phase chromatography on a Diol column and with hexane/ethyl acetate (50:50) as eluent. The analytes could be determined directly in the oil matrix, without need of a previous removal of the triglycerides. Normal phase LC ESI-MS with a makeup flow of polar modifier was used for checking the identity and purity of analyte peaks. Samples from 22 commercially available EPOs were analyzed. The average caffeoyl ester contents were 58 mg/100 g in cold pressed oils and 4.7 mg/100 g in partially raffinated oils. In fully raffinated EPO samples, the concentration was below the limit of detection. The influence of extraction temperature on the content of caffeoyl esters in nonraffinated EPO was investigated with seeds of Oenothera biennis and Oenothera lamarckiana, respectively. With O. lamarckiana, the concentration of caffeoyl esters in the oil increased with rising pressure and temperature, whereas no such dependency was found with O. biennis. Microscopic analysis revealed some differences in the histology of the seed testa, which may explain in part the differing behaviors in the extraction experiments. There was a difference between O. biennis and O. lamarckiana oils with respect to the relative amounts of the three esters. The temperature of the extraction process had no effect on the ratio of the compounds.  相似文献