Soil structure and soil hydraulic properties of Haplic Luvisol used as arable land and grassland     

Radka Kode&#x;ov  Veronika Jirk  Vít Kode&#x;  Marcela Mühlhanselov  Antonín Nikodem  Anna igov 《Soil & Tillage Research》2011,111(2):154-161

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Effects of residue location on soil organic matter turnover: results from an incubation experiment with 15N‐maize     

Anna Jacobs  Mirjam Helfrich  Jens Dyckmans  Rolf Rauber  Bernard Ludwig 《植物养料与土壤学杂志》2011,174(4):634-643

Differences in the mechanisms of storage and decomposition of organic matter (OM) between minimum tillage (MT) and conventional tillage (CT) are generally attributed to differences in the physical impact through tillage, but less is known about the effects of residue location. We conducted an incubation experiment at a water content of 60% of the maximum water‐holding capacity and 15°C with soils from CT (0–25 cm tillage depth) and MT fields (0–5 cm tillage depth) with ¹⁵N‐labeled maize straw incorporated to different depths (CT simulations: 0–15 cm; MT simulations: 0–5 cm) for 28 d in order to determine the effects of the tillage simulation on (1) mineralization of recently added residues, (2) the dynamics of macroaggregate formation and physical protection of OM, and (3) the partitioning of maize‐derived C and N within soil OM fractions. The MT simulations showed lower relative C losses, and the amount of maize‐C mineralized after 28 d of incubation was slightly but significantly lower in the MT simulations with maize added (MT_maize) than in the respective CT (CT_maize) simulations. The formation of new water‐stable macroaggregates occurred during the phase of the highest microbial activity, with a maximum peak 8 d after the start of incubation. The newly formed macroaggregates were an important location for the short‐term stabilization of C and N with a higher importance for MT_maize than for CT_maize simulations. In conclusion, our results suggest that a higher amount of OM in MT surface soils compared with CT surface soils may not only result from decreased macroaggregate destruction under reduced tillage but also from a higher efficiency of C retention due to a more concentrated residue input.  相似文献   

Demographic and socio-economic factors related to food intake and adherence to nutritional recommendations in a cohort of pre-school children     

Dubois L  Farmer A  Girard M  Burnier D  Porcherie M 《Public health nutrition》2011,14(6):1096-1104

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Transfer of learning after updating training mediated by the striatum     

Dahlin E  Neely AS  Larsson A  Bäckman L  Nyberg L 《Science (New York, N.Y.)》2008,320(5882):1510-1512

Process-specific training can improve performance on untrained tasks, but the magnitude of gain is variable and often there is no transfer at all. We demonstrate transfer to a 3-back test of working memory after 5 weeks of training in updating. The transfer effect was based on a joint training-related activity increase for the criterion (letter memory) and transfer tasks in a striatal region that also was recruited pretraining. No transfer was observed to a task that did not engage updating and striatal regions, and age-related striatal changes imposed constraints on transfer. These findings indicate that transfer can occur if the criterion and transfer tasks engage specific overlapping processing components and brain regions.  相似文献   

Spring-loaded mechanism of DNA unwinding by hepatitis C virus NS3 helicase     

Myong S  Bruno MM  Pyle AM  Ha T 《Science (New York, N.Y.)》2007,317(5837):513-516

NS3, an essential helicase for replication of hepatitis C virus, is a model enzyme for investigating helicase function. Using single-molecule fluorescence analysis, we showed that NS3 unwinds DNA in discrete steps of about three base pairs (bp). Dwell time analysis indicated that about three hidden steps are required before a 3-bp step is taken. Taking into account the available structural data, we propose a spring-loaded mechanism in which several steps of one nucleotide per adenosine triphosphate molecule accumulate tension on the protein-DNA complex, which is relieved periodically via a burst of 3-bp unwinding. NS3 appears to shelter the displaced strand during unwinding, and, upon encountering a barrier or after unwinding >18 bp, it snaps or slips backward rapidly and repeats unwinding many times in succession. Such repetitive unwinding behavior over a short stretch of duplex may help to keep secondary structures resolved during viral genome replication.  相似文献   

The draft genome of Ciona intestinalis: insights into chordate and vertebrate origins     

Dehal P  Satou Y  Campbell RK  Chapman J  Degnan B  De Tomaso A  Davidson B  Di Gregorio A  Gelpke M  Goodstein DM  Harafuji N  Hastings KE  Ho I  Hotta K  Huang W  Kawashima T  Lemaire P  Martinez D  Meinertzhagen IA  Necula S  Nonaka M  Putnam N  Rash S  Saiga H  Satake M  Terry A  Yamada L  Wang HG  Awazu S  Azumi K  Boore J  Branno M  Chin-Bow S  DeSantis R  Doyle S  Francino P  Keys DN  Haga S  Hayashi H  Hino K  Imai KS  Inaba K  Kano S  Kobayashi K  Kobayashi M  Lee BI  Makabe KW  Manohar C  Matassi G  Medina M  Mochizuki Y  Mount S 《Science (New York, N.Y.)》2002,298(5601):2157-2167

The first chordates appear in the fossil record at the time of the Cambrian explosion, nearly 550 million years ago. The modern ascidian tadpole represents a plausible approximation to these ancestral chordates. To illuminate the origins of chordate and vertebrates, we generated a draft of the protein-coding portion of the genome of the most studied ascidian, Ciona intestinalis. The Ciona genome contains approximately 16,000 protein-coding genes, similar to the number in other invertebrates, but only half that found in vertebrates. Vertebrate gene families are typically found in simplified form in Ciona, suggesting that ascidians contain the basic ancestral complement of genes involved in cell signaling and development. The ascidian genome has also acquired a number of lineage-specific innovations, including a group of genes engaged in cellulose metabolism that are related to those in bacteria and fungi.  相似文献   

Functional adaptation of BabA, the H. pylori ABO blood group antigen binding adhesin     

Aspholm-Hurtig M  Dailide G  Lahmann M  Kalia A  Ilver D  Roche N  Vikström S  Sjöström R  Lindén S  Bäckström A  Lundberg C  Arnqvist A  Mahdavi J  Nilsson UJ  Velapatiño B  Gilman RH  Gerhard M  Alarcon T  López-Brea M  Nakazawa T  Fox JG  Correa P  Dominguez-Bello MG  Perez-Perez GI  Blaser MJ  Normark S  Carlstedt I  Oscarson S  Teneberg S  Berg DE  Borén T 《Science (New York, N.Y.)》2004,305(5683):519-522

Adherence by Helicobacter pylori increases the risk of gastric disease. Here, we report that more than 95% of strains that bind fucosylated blood group antigen bind A, B, and O antigens (generalists), whereas 60% of adherent South American Amerindian strains bind blood group O antigens best (specialists). This specialization coincides with the unique predominance of blood group O in these Amerindians. Strains differed about 1500-fold in binding affinities, and diversifying selection was evident in babA sequences. We propose that cycles of selection for increased and decreased bacterial adherence contribute to babA diversity and that these cycles have led to gradual replacement of generalist binding by specialist binding in blood group O-dominant human populations.  相似文献   

Derivatives of erythropoietin that are tissue protective but not erythropoietic   总被引：1，自引：0，他引：1  

Leist M  Ghezzi P  Grasso G  Bianchi R  Villa P  Fratelli M  Savino C  Bianchi M  Nielsen J  Gerwien J  Kallunki P  Larsen AK  Helboe L  Christensen S  Pedersen LO  Nielsen M  Torup L  Sager T  Sfacteria A  Erbayraktar S  Erbayraktar Z  Gokmen N  Yilmaz O  Cerami-Hand C  Xie QW  Coleman T  Cerami A  Brines M 《Science (New York, N.Y.)》2004,305(5681):239-242

Erythropoietin (EPO) is both hematopoietic and tissue protective, putatively through interaction with different receptors. We generated receptor subtype-selective ligands allowing the separation of EPO's bioactivities at the cellular level and in animals. Carbamylated EPO (CEPO) or certain EPO mutants did not bind to the classical EPO receptor (EPOR) and did not show any hematopoietic activity in human cell signaling assays or upon chronic dosing in different animal species. Nevertheless, CEPO and various nonhematopoietic mutants were cytoprotective in vitro and conferred neuroprotection against stroke, spinal cord compression, diabetic neuropathy, and experimental autoimmune encephalomyelitis at a potency and efficacy comparable to EPO.  相似文献   

Ethics and refinement in animal research     

Olsson IA  Hansen AK  Sandøe P 《Science (New York, N.Y.)》2007,317(5845):1680

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Genome analysis reveals pili in Group B Streptococcus     

Lauer P  Rinaudo CD  Soriani M  Margarit I  Maione D  Rosini R  Taddei AR  Mora M  Rappuoli R  Grandi G  Telford JL 《Science (New York, N.Y.)》2005,309(5731):105

Pili are essential virulence factors in many Gram-negative bacteria; however, they have not been described in most important Gram-positive pathogens. While screening the sequence of multiple genomes of Group B Streptococcus, we identified protective antigens that formed high molecular weight polymers. Immunogold electron microscopy revealed that the structures have a pilus-like form. These large structures have gone unrecognized in decades of studies of Group B Streptococcus.  相似文献