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排序方式: 共有370条查询结果,搜索用时 31 毫秒
111.
Rauch A Thiel CT Schindler D Wick U Crow YJ Ekici AB van Essen AJ Goecke TO Al-Gazali L Chrzanowska KH Zweier C Brunner HG Becker K Curry CJ Dallapiccola B Devriendt K Dörfler A Kinning E Megarbane A Meinecke P Semple RK Spranger S Toutain A Trembath RC Voss E Wilson L Hennekam R de Zegher F Dörr HG Reis A 《Science (New York, N.Y.)》2008,319(5864):816-819
Fundamental processes influencing human growth can be revealed by studying extreme short stature. Using genetic linkage analysis, we find that biallelic loss-of-function mutations in the centrosomal pericentrin (PCNT) gene on chromosome 21q22.3 cause microcephalic osteodysplastic primordial dwarfism type II (MOPD II) in 25 patients. Adults with this rare inherited condition have an average height of 100 centimeters and a brain size comparable to that of a 3-month-old baby, but are of near-normal intelligence. Absence of PCNT results in disorganized mitotic spindles and missegregation of chromosomes. Mutations in related genes are known to cause primary microcephaly (MCPH1, CDK5RAP2, ASPM, and CENPJ). 相似文献
112.
Beck M Förster F Ecke M Plitzko JM Melchior F Gerisch G Baumeister W Medalia O 《Science (New York, N.Y.)》2004,306(5700):1387-1390
Nuclear pore complexes (NPCs) are gateways for nucleocytoplasmic exchange. To analyze their structure in a close-to-life state, we studied transport-active, intact nuclei from Dictyostelium discoideum by means of cryoelectron tomography. Subvolumes of the tomograms containing individual NPCs were extracted in silico and subjected to three-dimensional classification and averaging, whereby distinct structural states were observed. The central plug/transporter (CP/T) was variable in volume and could occupy different positions along the nucleocytoplasmic axis, which supports the notion that it essentially represents cargo in transit. Changes in the position of the CP/T were accompanied by structural rearrangements in the NPC scaffold. 相似文献
113.
Mitral cells (MCs) in the olfactory bulb (OB) respond to odors with slow temporal firing patterns. The representation of each odor by activity patterns across the MC population thus changes continuously throughout a stimulus, in an odor-specific manner. In the zebrafish OB, we found that this distributed temporal patterning progressively reduced the similarity between ensemble representations of related odors, thereby making each odor's representation more specific over time. The tuning of individual MCs was not sharpened during this process. Hence, the individual responses of MCs did not become more specific, but the odor-coding MC assemblies changed such that their overlap decreased. This optimization of ensemble representations did not occur among olfactory afferents but resulted from OB circuit dynamics. Time can therefore gradually optimize stimulus representations in a sensory network. 相似文献
114.
Michaelis W Seifert R Nauhaus K Treude T Thiel V Blumenberg M Knittel K Gieseke A Peterknecht K Pape T Boetius A Amann R Jørgensen BB Widdel F Peckmann J Pimenov NV Gulin MB 《Science (New York, N.Y.)》2002,297(5583):1013-1015
Massive microbial mats covering up to 4-meter-high carbonate buildups prosper at methane seeps in anoxic waters of the northwestern Black Sea shelf. Strong 13C depletions indicate an incorporation of methane carbon into carbonates, bulk biomass, and specific lipids. The mats mainly consist of densely aggregated archaea (phylogenetic ANME-1 cluster) and sulfate-reducing bacteria (Desulfosarcina/Desulfococcus group). If incubated in vitro, these mats perform anaerobic oxidation of methane coupled to sulfate reduction. Obviously, anaerobic microbial consortia can generate both carbonate precipitation and substantial biomass accumulation, which has implications for our understanding of carbon cycling during earlier periods of Earth's history. 相似文献
115.
Tomaszewska E Hebert VR Brunner JF Jones VP Doerr M Hilton R 《Journal of agricultural and food chemistry》2005,53(7):2399-2405
Pome fruit growers and crop consultants have expressed concerns about the seasonal release performance of commercial codling moth mating disruption dispenser products. Because of these concerns, we developed a laboratory flow-through volatile collection system (VCS) for measuring the volatile release of the codling moth sex pheromone, codlemone, from commercially available hand-applied dispensers. Under controlled air-flow and temperature conditions, the released vapor was trapped onto a polyurethane foam adsorbent followed by solvent extraction, solvent reduction, and GC/MS determination. Method recovery and breakthrough validations were performed to demonstrate system reliability before determining codlemone release from commercial dispensers field-aged over 140 days. The volatile collection was carried out in a consistent manner among five dispenser types most commonly used by growers, so that direct comparison of performance could be made. The comparison showed differences in the amount of pheromone released and in the patterns of release throughout the season between dispenser types. The variation in release performance demonstrates the need for routine evaluation of commercially marketed mating disruption dispensers. We believe that the simple and cost-effective volatile collection system can assist pheromone dispenser manufacturers in determining seasonal dispenser performance before new products are introduced into the commercial market and in rapidly verifying dispenser release when field-aged dispenser efficacy is in question. 相似文献
116.
117.
Torsten Vor Jens Dyckmans Norman Loftfield Friedrich Beese Heiner Flessa 《植物养料与土壤学杂志》2003,166(1):39-45
The availability of O2 is one of the most important factors controlling the chemical and biological reactions in soils. In this study, the effects of different aeration conditions on the dynamics of the emission of trace gases (CO2, N2O, CH4) and the leachate composition (NO3‐, DOC, Mn, Fe) were determined. The experiment was conducted with naturally structured soil columns (silty clay, Vertisol) from a well aerated forest site. The soil monoliths were incubated in a microcosm system at different O2 concentrations (0, 0.001, 0.005, 0.01, 0.05, and 0.205 m3 m‐3 in the air flow through the headspace of the microcosms) for 85 days. Reduced O2 availability resulted in a decreased CO2 release but in increased N2O emission rates. The greatest cumulative N2O emissions (= 1.6 g N2O‐N m‐2) were observed at intermediate O2 concentrations (0.005 and 0.01 m3 m‐3) when both nitrification and denitrification occurred simultaneously in the soil. Cumulative N2O emissions were smallest (= 0.05 g N2O‐N m‐2) for the aeration with ambient air (O2 concentration: 0.205 m3 m‐3), although nitrate availability was greatest in this treatment. The emission of CH4 and leaching of Mn and Fe were restricted to the soil columns incubated under completely anoxic conditions. The sequence of the reduction processes under completely anoxic conditions complied with the thermodynamic theory: soil nitrate was reduced first, followed by the reduction of Mn(IV) and Fe(III) and finally CO2 was reduced to CH4. The re‐aeration of the soil columns after 85 days of anoxic incubation terminated the production of CH4 and dissolved Fe and Mn in the soil but strongly increased the emission rates of CO2 and N2O and the leaching of NO3‐ probably because of the accumulation of DOC and NH4+ during the previous anoxic period. 相似文献
118.
The estimation of acidic deposition strongly depends on the availability of accurate emission data. The atmospheric models, that calculate concentrations and depositions of pollutants, need data in a high temporal resolution (e.g. daily, 6-hourly or even hourly data). However, although some progress has been achieved concerning annual emission data for Europe (e.g. CORINAIR 90), only very little information is available about the temporal variation of these emissions during a year. Therefore, within the EUROTRAC-GENEMIS project special emphasis was laid on the development of methods to generate emissions with a high temporal and spatial resolution. As results the temporal and spatial distribution of SO2- and NOX-emissions are shown. The results indicate, that the emissions vary considerably over time and that the use of simple patterns for the temporal disaggregation is not sufficient for modelling and assessment of acidic deposition. 相似文献
119.
Prediction of deoxynivalenol and zearalenone concentrations in Fusarium graminearum inoculated backcross populations of maize by symptom rating and near‐infrared spectroscopy
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Thomas Miedaner Sen Han Bettina Kessel Milena Ouzunova Tobias Schrag Friedrich H. Utz Albrecht E. Melchinger 《Plant Breeding》2015,134(5):529-534
Gibberella ear rot (GER) caused by Fusarium graminearum is a destructive disease in maize of temperate regions resulting in yield reduction and contamination by the mycotoxins deoxynivalenol (DON) and zearalenone (ZON). We wanted to analyse whether prediction of DON and ZON concentrations is feasible either by GER severity ratings or by near‐infrared spectroscopy (NIRS). We analysed 80 and 102 lines developed by backcrossing doubled‐haploid lines from segregating populations to the resistant and susceptible parent, respectively, by artificial infection at three locations in Germany and France. Both backcross (BC) populations differed substantially in their means for all traits with significant (P < 0.01) genotypic variances. DON and ZON concentrations measured by immunotests were significantly (P < 0.01) correlated with each other and with GER severity within each BC population (0.6 ≤ r ≤ 0.9, P < 0.01). DON concentration measured by immunotest and NIRS significantly correlated (r ≈ 0.9, P < 0.01). In conclusion, DON and ZON concentrations could be reliably predicted by GER severity. Additional NIRS analysis of DON concentration might be useful for the positively selected fraction. 相似文献
120.