Impacts of 120 years of fertilizer addition on a temperate grassland ecosystem.

The widespread application of fertilizers has greatly influenced many processes and properties of agroecosystems, and agricultural fertilization is expected to increase even further in the future. To date, most research on fertilizer impacts has used short-term studies, which may be unrepresentative of long-term responses, thus hindering our capacity to predict long-term impacts. Here, we examined the effects of long-term fertilizer addition on key ecosystem properties in a long-term grassland experiment (Palace Leas Hay Meadow) in which farmyard manure (FYM) and inorganic fertilizer treatments have been applied consistently for 120 years in order to characterize the experimental site more fully and compare ecosystem responses with those observed at other long-term and short-term experiments. FYM inputs increased soil organic carbon (SOC) stocks, hay yield, nutrient availability and acted as a buffer against soil acidification (>pH 5). In contrast, N-containing inorganic fertilizers strongly acidified the soil (

Competition between plant and bacterial cells at the microscale regulates the dynamics of nitrogen acquisition in wheat (Triticum aestivum).

The ability of plants to compete effectively for nitrogen (N) resources is critical to plant survival. However, controversy surrounds the importance of organic and inorganic sources of N in plant nutrition because of our poor ability to visualize and understand processes happening at the root-microbial-soil interface. Using high-resolution nano-scale secondary ion mass spectrometry stable isotope imaging (NanoSIMS-SII), we quantified the fate of ¹5N over both space and time within the rhizosphere. We pulse-labelled the soil surrounding wheat (Triticum aestivum) roots with either ¹5NH4⁺ or ¹5N-glutamate and traced the movement of ¹5N over 24 h. Imaging revealed that glutamate was rapidly depleted from the rhizosphere and that most ¹5N was captured by rhizobacteria, leading to very high ¹5N microbial enrichment. After microbial capture, approximately half of the ¹5N-glutamate was rapidly mineralized, leading to the excretion of NH4⁺, which became available for plant capture. Roots proved to be poor competitors for ¹5N-glutamate and took up N mainly as ¹5NH4⁺. Spatial mapping of ¹5N revealed differential patterns of ¹5N uptake within bacteria and the rapid uptake and redistribution of ¹5N within roots. In conclusion, we demonstrate the rapid cycling and transformation of N at the soil-root interface and that wheat capture of organic N is low in comparison to inorganic N under the conditions tested.

Application of nanoscale secondary ion mass spectrometry to plant cell research.

Imaging resource flow in soil-plant systems remains central to understanding plant development and interactions with the environment. Typically, subcellular resolution is required to fully elucidate the compartmentation, behavior, and mode of action of organic compounds and mineral elements within plants. For many situations this has been limited by the poor spatial resolution of imaging techniques and the inability to undertake studies in situ. Here we demonstrate the potential of Nanoscale Secondary Ion Mass Spectrometry (NanoSIMS), which is capable of the quantitative high-resolution spatial imaging of stable isotopes (e.g. (12) C, (13) C, (14) N, (15) N, (16) O, (18) O, (31) P, (34) S) within intact plant-microbial-soil systems. We present examples showing how the approach can be used to investigate competition for (15) N-labeled nitrogen compounds between plant roots and soil microorganisms living in the rhizosphere and the spatial imaging of (31) P in roots. We conclude that NanoSIMS has great potential to elucidate the flow of isotopically-labeled compounds in complex media (e.g. soil) and opens up countless new opportunities for studying plant responses to abiotic stress (e.g. (18) O3, elevated (13) CO2), signal exchange, nutrient flow and plant-microbial interactions.

In situ mapping of nutrient uptake in the rhizosphere using nanoscale secondary ion mass spectrometry.

Plant roots and microorganisms interact and compete for nutrients within the rhizosphere, which is considered one of the most biologically complex systems on Earth. Unraveling the nitrogen (N) cycle is key to understanding and managing nutrient flows in terrestrial ecosystems, yet to date it has proved impossible to analyze and image N transfer in situ within such a complex system at a scale relevant to soil-microbe-plant interactions. Linking the physical heterogeneity of soil to biological processes marks a current frontier in plant and soil sciences. Here we present a new and widely applicable approach that allows imaging of the spatial and temporal dynamics of the stable isotope (15)N assimilated within the rhizosphere. This approach allows visualization and measurement of nutrient resource capture between competing plant cells and microorganisms. For confirmation we show the correlative use of nanoscale secondary ion mass spectrometry, and transmission electron microscopy, to image differential partitioning of (15)NH(4)(+) between plant roots and native soil microbial communities at the submicron scale. It is shown that (15)N compounds can be detected and imaged in situ in individual microorganisms in the soil matrix and intracellularly within the root. Nanoscale secondary ion mass spectrometry has potential to allow the study of assimilatory processes at the submicron level in a wide range of applications involving plants, microorganisms, and animals.

A phase II study of irinotecan in children with relapsed or refractory neuroblastoma: a European cooperation of the Société Française d'Oncologie Pédiatrique (SFOP) and the United Kingdom Children Cancer Study Group (UKCCSG).

PURPOSE: To evaluate the efficacy and safety of irinotecan in paediatric recurrent or refractory neuroblastoma. PATIENTS AND METHODS: Thirty seven patients aged between 6 months and < or = 20 years, with relapsed or refractory neuroblastoma, received irinotecan at 600 mg/m(2) administered as a 60-min infusion, every 3 weeks. Tumour response was evaluated by conventional radiological and mIBG scans every two cycles. RESULTS: No objective response was observed during the study. Stable disease was observed in 13% of evaluable patients. Median times to progression and survival were 1.4 months (range, 1.2-1.5 months) and 8.8 months (range, 6.7-11.3 months), respectively. One forty two cycles were administered, with a median of two cycles per patient (range, 1-17 cycles). The most common grade 3-4 toxicities were neutropenia (65% of patients), anaemia (43%), thrombocytopenia (38%), vomiting (14%), abdominal pain or cramping (8%), and nausea (5%). CONCLUSION: Irinotecan administered intravenously as a single agent every 3 weeks induced no objective response in relapsed or refractory neuroblastoma.

Phase II trial of irinotecan in children with relapsed or refractory rhabdomyosarcoma: a joint study of the French Society of Pediatric Oncology and the United Kingdom Children's Cancer Study Group.

PURPOSE: This phase II study was designed to evaluate the efficacy of irinotecan administered intravenously once every 3 weeks in pediatric patients with recurrent or refractory rhabdomyosarcoma. PATIENTS AND METHODS: A total of 35 patients younger than age 20 years, with refractory or relapsed rhabdomyosarcoma for which standard treatments have failed, received irinotecan at 600 mg/m2 administered as a 60-minute infusion every 3 weeks. Concomitant treatments included atropine for cholinergic symptoms, loperamide for diarrhea at the first liquid stool, and preventive antiemetic treatment. Tumor response was assessed every two cycles until progression according to WHO criteria. RESULTS: The best overall response rate to irinotecan was 11.4% (95% CI, 3.2 to 26.7%; 2.9% complete responses, 8.5% partial responses) from all patients recruited. The median times to progression and survival were 1.4 and 5.8 months, respectively. A total of 112 cycles were administered, with a median number of two cycles per patient (range, 1 to 16). The most common grade 3/4 toxicities were neutropenia (46%), abdominal pain or cramping (17%), cholinergic syndrome (14%), nausea/vomiting (11%), anemia (11%), thrombocytopenia (9%), and diarrhea (6%). CONCLUSION: In heavily pretreated children with a high tumor burden who have been treated with multiagent chemotherapy, irinotecan administered intravenously as a single agent, at 600 mg/m2 every 3 weeks, showed an interesting objective response rate and a good tolerance profile in rhabdomyosarcoma.

A novel method for the study of the biophysical interface in soils using nano-scale secondary ion mass spectrometry.

The spatial location of microorganisms and their activity within the soil matrix have major impacts on biological processes such as nutrient cycling. However, characterizing the biophysical interface in soils is hampered by a lack of techniques at relevant scales. A novel method for studying the distribution of microorganisms that have incorporated isotopically labelled substrate ('active' microorganisms) in relation to the soil microbial habitat is provided by nano-scale secondary ion mass spectrometry (NanoSIMS). Pseudomonas fluorescens are ubiquitous in soil and were therefore used as a model for 'active' microorganisms in soil. Batch cultures (NCTC 10038) were grown in a minimal salt medium containing 15N-ammonium sulphate (15/14N ratio of 1.174), added to quartz-based white sand or soil (coarse textured sand), embedded in Araldite 502 resin and sectioned for NanoSIMS analysis. The 15N-enriched P. fluorescens could be identified within the soil structure, demonstrating that the NanoSIMS technique enables the study of spatial location of microbial activity in relation to the heterogeneous soil matrix. This technique is complementary to the existing techniques of digital imaging analysis of soil thin sections and scanning electron microscopy. Together with advanced computer-aided tomography of soils and mathematical modelling of soil heterogeneity, NanoSIMS may be a powerful tool for studying physical and biological interactions, thereby furthering our understanding of the biophysical interface in soils.