High Background Levels Research Articles

Analysis of Clusterin Glycoforms in the Urine of BSE-Infected Fleckvieh–Simmental Cows

Currently approved tests for bovine spongiform encephalopathy (BSE) monitoring in cattle are based on the detection of the disease-related isoform of the prion protein in brain tissue and consequently are only suitable for postmortem diagnosis. Previously, to meet the demand for an antemortem test based on a matrix that would permit easy access and repeated sampling, two-dimensional differential gel electrophoresis (2D-DIGE) was used to perform an unbiased screen of bovine urine. Data demonstrated the altered abundance of particular isoforms of the multifunctional glycoprotein clusterin in urine samples obtained from BSE-infected and age-matched Fleckvieh–Simmental cattle. Unfortunately, the use of particular isoforms of a relatively abundant urine protein such as clusterin for diagnosis faces many of the same challenges encountered in tests based on PrPd detection. In both instances the specific detection of the marker protein is complicated by the high background levels of proteins with identical amino acid sequences, but lacking the disease-specific posttranslational modifications or configuration. The goal of the current study was to define the distinguishing characteristics of the clusterin isoforms observed. Biochemical and mass spectrometry analyses in combination with the generation of bovine clusterin subunit-specific antibodies enabled us to demonstrate that it was β-subunits of clusterin possessing N-linked glycans of complex structure that exhibited differential abundance in response to BSE infection. The charateristic highly glycosylated clusterin β-subunit was detectable as early as 16 mo post infection (mpi) by one-dimensional (1D) Western blot analysis of urine obtained from BSE-infected cattle.

Optical imaging with dynamic contrast agents.

Biological imaging applications often employ molecular probes or nanoparticles for enhanced contrast. However, resolution and detection are still often limited by the intrinsic heterogeneity of the sample, which can produce high levels of background that obscure the signals of interest. Herein, we describe approaches to overcome this obstacle based on the concept of dynamic contrast: a strategy for elucidating signals by the suppression or removal of background noise. Dynamic contrast mechanisms can greatly reduce the loading requirement of contrast agents, and may be especially useful for single-probe imaging. Dynamic contrast modalities are also platform-independent, and can enhance the performance of sophisticated biomedical imaging systems or simple optical microscopes alike. Dynamic contrast is performed in two stages: 1) a signal modulation scheme to introduce time-dependent changes in amplitude or phase, and 2) a demodulation step for signal recovery. Optical signals can be coupled with magnetic nanoparticles, photoswitchable probes, or plasmon-resonant nanostructures for modulation by magnetomotive, photonic, or photothermal mechanisms, respectively. With respect to image demodulation, many of the strategies developed for signal processing in electronics and communication technologies can also be applied toward the editing of digital images. The image-processing step can be as simple as differential imaging, or may involve multiple reference points for deconvolution by using cross-correlation algorithms. Periodic signals are particularly amenable to image demodulation strategies based on Fourier transform; the contrast of the demodulated signal increases with acquisition time, and modulation frequencies in the kHz range are possible. Dynamic contrast is an emerging topic with considerable room for development, both with respect to molecular or nanoscale probes for signal modulation, and also to methods for more efficient image processing and editing.

Knowledge and Demand for Information about Islet Transplantation in Patients with Type 1 Diabetes

This cross-sectional study based on self-administrated questionnaire was conducted to investigate knowledge, related factors, and sources of information regarding islet transplantation in patients with type 1 diabetes in Japan. Among 137 patients who provided valid responses, 67 (48.9%) knew about islet transplantation. Their main source of information was newspapers or magazines (56.7%) and television or radio (46.3%). However, 85.8% of patients preferred the attending physician as their source of information. Although more than half of the patients were correctly aware of issues related to islet transplantation, the following specific issues for islet transplantation were not understood or considered, and there was little knowledge of them: need for immunosuppressants, lifestyle and dietary adaptations, fewer bodily burdens, and complications. The experience of hypoglycaemia, a high level of academic background, frequent self-monitoring of blood glucose, and the use of continuous subcutaneous insulin infusion were related to higher knowledge about islet transplantation.

Study of distribution of radionuclides in cultivated land in and around chikmagalur, Karnataka, India

Cultivation of land modifies soil characteristics and influences redistribution of radionuclides in topsoil. The concentrations of 210 Po and 210 Pb in the cultivated land of Chikmagalur were measured by wet ashing silver planchet electroplating alpha count method. The concentration of 226 Ra was determined using Emanometry Method. The samples were precipitated by chemical processes and the concentrations of 228 Ra measured using high efficiency low level background gas flow beta counter. The lowest activity of 226 Ra, 228 Ra 210 Po and 210 Pb recorded at study area were 6.1, 5.6, 12.9 and 20.6 Bq.Kg -1 and maxima were 47.7, 29.6, 71.2 and 120.5 Bq.Kg -1 and mean 13.8, 19.2, 28.6 and 1.8 Bq.Kg -1 respectively. The mean of ratios of 210 Po and 210 Pb in cultivated and uncultivated land were found to be 0.53 and 1.06 respectively. Concentrations of 226 Ra, 228 Ra and 210 Po in cultivated land found to be lower than that of undisturbed land but reverse in case of 210 Pb. Decrease in activities of 226 Ra, 228 Ra, and 210 Po in cultivated may due to wash out of 'floating fraction' with rainwater and the increase of activity of 210 Pb may be due to re-suspension. The 're-suspension factor' (K) increases for 226 Ra, 228 Ra, and 210 Po in cultivated and fertilizer added area, but not for 210 Pb. Also the concentrations of radionuclides were found to be high in comparison with global and Indian average.

Long-range atmospheric transport of persistent organochlorinated compounds from south and mainland south-eastern Asia to a remote mountain site in south-western China

A range of organochlorinated compounds have been consumed in China, India and the countries of mainland southeast Asia (MSA). Considering their persistence in the environment and ability in long-range atmospheric transport (LRAT), the potential outflow of these compounds from this region is therefore of great concern in the context of the global distribution of toxic chemicals. As part of a monitoring campaign aimed at investigating the LRAT of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) from southern China, MSA and northern India, atmospheric levels of OCPs and PCBs were measured once a week from October 2005 through December 2006 at Tengchong Mountain (TM), a remote site located in south-western China. The average concentrations of OCPs were found to be higher than those in other remote stations in the Arctic and the Tibetan plateau, except for α-hexachlorocyclohexane (α-HCH). A high level of β-HCH and low α-HCH/β-HCH ratio was attributed to an accidental release of β-HCH from unknown sources, besides obvious evidence of lindane (γ-HCH) and technical HCH usage. Temporal variations of chlordanes and endosulfan were related to the usage pattern of these compounds, as well as LRAT. In contrast, dichlorodiphenyltrichloroethane (DDT) exhibited a relatively minor seasonal variation. The OCP levels at the monitoring site were found to be related to the air parcel back trajectories on the basis of four distinct clusters. Elevated levels of HCHs and DDTs were observed when air parcels originated from northern India where considerable OCP usage was reported recently, while high levels of γ-HCH and TC (trans-chlordane) were mainly associated with air masses from southern China and northern MSA. The study highlighted the high background level of OCPs as well as their temporal patterns of trans-boundary LRAT in the MSA region.

Screen and confirmation of PEG‐epoetin β in equine plasma

Methods have been developed to screen for and confirm darbepoetin alfa, recombinant human EPO, and methoxy polyethylene glycol-epoetin β (PEG-epoetin β) in horse plasma. All three methods screen samples with an enzyme-linked immunosorbent assay (ELISA) and confirm by liquid chromatography-tandem mass spectrometry (LC-MS/MS). This report focuses on PEG-epoetin β. The ELISA assay was able to detect PEG-epoetin β at 0.02 ng/mL in 50 µL of horse plasma. Many samples had high background levels of immunoreactivity; however, introducing polyethylene glycol 6000 (PEG 6000) into the samples before the ELISA assay removed the high background and increased the apparent concentrations of PEG-epoetin β. In samples collected following the administration of 100 µg of PEG-epoetin β by the intravenous (IV), intramuscular (IM) and subcutaneous (SC) routes, PEG-epoetin β was detectable up to 72, 144, and 120 h, respectively. The samples were prepared for LC-MS/MS analysis by extraction with anti-rHuEPO-antibodies-coated Dynabeads followed by digestion with trypsin. The LC-MS/MS confirmation method used the multiple reaction monitoring (MRM) scan mode to monitor four precursor-product ion transitions of the EPO-derived peptide T₆. All four transitions of T₆ were detectable with S/N > 3. The limit of confirmation for PEG-epoetin β was 1.0 ng/mL in 2 mL of horse plasma. The method successfully confirmed the presence of PEG-epoetin β in a sample collected from a Mircera®-treated horse. Compared to PEG-epoetin β, better sensitivity was achieved for darbepoetin alfa and recombinant human EPO. Darbepoetin alfa was detected in horse plasma four days after IM administration of 100 µg.

High-Throughput Sequencing of the Human Platelet Transcriptome

AbstractAbstract 481Most successful DNA-based genome wide association studies identify genomic regions, not genes themselves, and the findings are often devoid of context or mechanism. To identify the genetic basis of disease and disease traits, it is imperative to characterize the quantity and forms of the genes that are expressed in the tissue of interest. It is not feasible to use primary megakaryocytes to profile mRNA from large numbers of subjects, but platelet RNA is easy to obtain. Others and we have previously surveyed genome-wide platelet RNA expression using microarrays, an approach that has had a major impact on systems biology. However, microarrays have a number of limitations, including the use of probes only to known transcripts, a limited dynamic range for quantifying very low and high levels of transcripts, high background levels from cross-hybridization, and complicated normalization schemes to compare expression levels across experiments. Novel high-throughput sequencing approaches that overcome the limitations of microarrays have recently become available. RNA sequencing (RNAseq) has a remarkable ability to quantify mRNAs and provide information about transcript sequence variations, including single nucleotide changes and alternately spliced exons. The goal of these studies was to apply RNAseq to capture platelet transcriptome complexity. Total RNA was prepared using leukocyte-depleted platelets (LDP; less than 1 WBC per 5 million platelets) from 4 donors; 2 were studied twice each. Analysis of this material showed that compared to nucleated cells (HeLa, Meg-01), platelets had 50%-90% less ribosomal RNA, and high levels of messenger and small RNAs (Agilent 2100). The major reduction in platelet rRNA was confirmed by RNA gel analysis. The platelet whole transcriptomes were analyzed via the Applied Biosystems (AB) SOLiD 3Plus next generation sequencing protocols and platform. A typical sequence run generated ∼250 million reads of 50 bp each. We observed more than 30,000 independent platelet mRNA-coding transcripts from about 10,000 genes, demonstrating substantial numbers of variant isoforms. The increased sensitivity of RNAseq for low copy number is clear from these results, because prior platelet transcriptome studies using microarrays have identified only 1500–6000 expressed genes. As an example, the platelet-specific transcript, ITGA2B, showed very high copy number in platelets, but no expression in HeLa cells and modest expression in the megakaryocyte cell line, Meg-01. As is expected for RNA-Seq data, the density of mapped reads varies by exon and local sequence. We also provide examples of newly discovered SNPs that encode non-conservative amino acid changes (AKT2 1209A/T; PIK3CB 837C/G) and alter consensus exon/intron splice junction sites (P2YR12 nt 65 G/A). We have also identified a major difference in the ratio of two splice variants of the FcRg chain, 4:1 in one human platelet donor and 49:1 in another. In summary, we have demonstrated that RNAseq can accurately and sensitively determine the quantity and quality of variations in individual platelet transcriptomes. It appears that the the platelet transcriptome is approximately 10 times more complex than previously thought. The major relative reduction in platelet rRNA may be an advantage for characterizing functional platelet transcripts. RNAseq should permit better understanding of the molecular mechanisms regulating platelet physiology and identify novel genetic variants that contribute to disorders of thrombosis and hemostasis. Disclosures:No relevant conflicts of interest to declare.

Seasonal variations of aerosol size distributions based on long-term measurements at the high altitude Himalayan site of Nepal Climate Observatory-Pyramid (5079 m), Nepal

Abstract. The present paper investigates the diurnal and seasonal variability of the aerosol total number concentration, number and volume size distribution between 10 nm and 10 μm, from a combination of a scanning mobility particle sizer (SMPS) and an optical counter (OPC), performed over a two-year period (January 2006–February 2008) at the Nepal Climate Observatory-Pyramid (NCO-P) research station, (5079 m a.s.l.). The annual average number concentration measured over the two-year period at the NCO-P is 860 cm−3. Total concentrations show a strong seasonality with maxima during pre-monsoon and post-monsoon seasons and minima during the dry and monsoon seasons. A diurnal variation is also clearly observed, with maxima between 09:00 and 12:00 UTC. The aerosol concentration maxima are mainly due to nucleation processes during the post-monsoon season, as witnessed by high nucleation mode integrated number concentrations, and to transport of high levels of pollution from the plains by valley breezes during the pre-monsoon season, as demonstrated by high accumulation mode integrated number concentrations. Night-time number concentration of particles (from 03:00 to 08:00 NST) are relatively low throughout the year (from 450 cm−3 during the monsoon season to 675 cm−3 during the pre-monsoon season), indicating the of high altitudes background level, as a result of downslope winds during this part of the day. However, it was found that these background concentrations are strongly influenced by the daytime concentrations, as they show the same seasonal variability. If nighttime concentrations were presumed to be representative of free troposphere (FT)/residual layer concentrations, they would be found to be two times higher than at other lower altitudes European sites, such as the Jungfraujoch. However, BL intrusions might contaminate the free troposphere/residual layer even at this altitude, especially during regional air masses influence. Night-time measurements were subsequently selected to study the FT composition according to different air masses, and the effect of long range transport to the station.

Total mercury in wild fish in Guizhou reservoirs, China

The health hazard of mercury (Hg) compounds is internationally recognized, and the main pathways for methylmercury (MeHg) intake in humans are through consumption of food, especially fish. Given the large releases of Hg to the environment in China, combined with the fast development of hydropower, this issue deserves attention. Provided similar mobilization pathways of Hg in China as seen in reservoirs in North America and Europe one should expect increased Hg contamination in relation to future hydropower reservoir construction in this country. This study presents total Hg (THg) concentrations in wild fish from six Guizhou reservoirs, China. The THg concentrations in fish were generally low despite high background levels in the bedrock and depositions from local point sources. The over all mean ± SD concentration of THg was (0.066 ± 0.078) μg/g ( n = 235). After adjusting for among-reservoir variation in THg, there were significant differences in THg among functional groups of the fish, assumed to reflect trophic levels. Predicted THg-concentration ratios, retrieved from a mixed linear model, between the functional groups were 9:4:4:1 for carnivorous, omnivorous, planktivorous and herbivorous fish. This result indicated that MeHg accumulation may prevail even under circumstances with short food chains as in this Chinese water system. No fish exceeded recommended maximum THg limit for human consumption set by World Health Organization and the Standardization Administration of China (0.5 μg/g fish wet weight (ww)). Only six fish (2.5%) exceeded the maximum THg limit set by US Environmental Protection Agency (0.3 μg/g fish ww).

Human Lung Cancer Risks from Radon – Part II – Influence from Combined Adaptive Response and Bystander Effects – a Microdose Analysis

In the prior Part I, the potential influence of the low level alpha radiation induced bystander effect (BE) on human lung cancer risks was examined. Recent analysis of adaptive response (AR) research results with a Microdose Model has shown that single low LET radiation induced charged particles traversals through the cell nucleus activates AR. We have here conducted an analysis based on what is presently known about adaptive response and the bystander effect (BE) and what new research is needed that can assist in the further evaluation human cancer risks from radon. We find that, at the UNSCEAR (2000) worldwide average human exposures from natural background and man-made radiations, the human lung receives about a 25% adaptive response protection against the radon alpha bystander damage. At the UNSCEAR (2000) minimum range of background exposure levels, the lung receives minimal AR protection but at higher background levels, in the high UNSCEAR (2000) range, the lung receives essentially 100% protection from both the radon alpha damage and also the endogenic, spontaneously occurring, potentially carcinogenic, lung cellular damage.

Convex Lens-Induced Confinement for Imaging Single Molecules

Fluorescence imaging is used to study the dynamics of a wide variety of single molecules in solution or attached to a surface. Two key challenges in this pursuit are (1) to image immobilized single molecules in the presence of a high level of fluorescent background and (2) to image freely diffusing single molecules for long times. Strategies that perform well by one measure often perform poorly by the other. Here, we present a simple modification to a wide-field fluorescence microscope that addresses both challenges and dramatically improves single-molecule imaging. The technique of convex lens-induced confinement (CLIC) restricts molecules to a wedge-shaped gap of nanoscale depth, formed between a plano-convex lens and a planar coverslip. The shallow depth of the imaging volume leads to 20-fold greater rejection of background fluorescence than is achieved with total internal reflection fluorescence (TIRF) imaging. Elimination of out-of-plane diffusion leads to an approximately 10,000-fold longer diffusion-limited observation time per molecule than is achieved with confocal fluorescence correlation spectroscopy. The CLIC system also provides a new means to determine molecular size. The CLIC system does not require any nanofabrication, nor any custom optics, electronics, or computer control.

Validating 123I-metaiodobenzylguanidine as a platelet marker for non-invasive imaging in rabbits

Introduction Recent in vitro studies in our laboratory have demonstrated that platelets are necessary for leukocyte recruitment and airway remodelling in models of allergic airway inflammation, and also migrate to lung tissues in response to anti-IgE or relevant allergens in allergic asthma. Non-invasive imaging of platelet migration in vivo would provide a further insight into the roles of platelets in inflammatory diseases such as asthma, and metaiodobenzylguanidine (MIBG) was considered as a suitable platelet marker. Methods The kinetics of MIBG uptake into rabbit platelets, the effect of MIBG on platelet function and the effect of platelet activation on MIBG uptake and retention were investigated. MIBG-labelled platelets were administered intravenously into rabbits and the time course of radioactivity in the lung and blood was monitored as a function of stimulation. Results Following a 4 h incubation of MIBG in rabbit PRP, a near maximal MIBG uptake (52.4 ± 20.2%) in platelets occurred. This time point was chosen for subsequent in vitro studies. In vitro platelet function studies showed that MIBG has no effect on ADP or PAF-induced platelet aggregation, PAF-induced thromboxane production or fMLP-induced platelet chemotaxis. However, serotonin showed a significant effect on MIBG uptake and retention, but only at high concentrations. Stimulation of rabbit platelets with ADP and PAF caused a significant release of stored MIBG in vitro. Following i.v. administration of MIBG labelled platelets, the response to i.v. ADP and PAF stimulation was small but significant. Discussion The release of MIBG from platelets in vivo, particularly following stimulation, leads to high background levels. Therefore, MIBG may have limited utility as a label for imaging platelets in vivo using PET. However, it may be a useful marker in detecting pathological conditions where platelet migration is involved.

Muon identification procedure for the ATLAS detector at the LHC using Muonboy reconstruction package and tests of its performance using cosmic rays and single beam data

ATLAS is one of the four experiments at the Large Hadron Collider (LHC) at CERN. This experiment has been designed to study a large range of physics including searches for previously unobserved phenomena such as the Higgs Boson and super-symmetry. The ATLAS Muon Spectrometer (MS) is optimized to measure final state muons in a large momentum range, from a few GeV up to TeV. Its momentum resolution varies from (2-3%) at 10-100 GeV/c to 11% at 1 TeV, taking into account the high level background environment, the inhomogeneous magnetic field, and the large size of the apparatus (24 m diameter by 44 m length). A robust muon identification and high momentum measurement accuracy is crucial to fully exploit the physics potential of the LHC.The basic principles of the muon reconstruction packages Muonboy, STACO, MuTag are discussed in this paper. Details of the modifications done in order to adapt the pattern recognition to the cosmic-ray configuration as well as its performance with the recent cosmic-rays and single beam data are presented.

GMR biosensor arrays: Correction techniques for reproducibility and enhanced sensitivity

Giant magnetoresistive biosensors possess great potential in biomedical applications for quantitatively detecting magnetically tagged biomolecules. Magnetic sensing does not suffer from the high background levels found in optical sensing modalities such as the enzyme linked immunosorbent assay translating into a technology with higher sensitivity. However, to reveal the full potential of these sensors and compensate for non-idealities such as temperature dependence, digital correction and calibration techniques are not only useful but imperative. Using these calibration techniques to correct for process variations and dynamic changes in the sensing environment (such as temperature and magnetic field), we are able to obtain extremely sensitive and, more importantly, reproducible results for quantifiable biomolecular reorganization. The reproducibility of the system was improved by over 3× using digital correction techniques and the sensors are made temperature independent by using a novel background correction technique.

Sorbitol-fermenting Bifidobacteria are indicators of very recent human faecal pollution in streams and groundwater habitats in urban tropical lowlands.

Sorbitol-fermenting Bifidobacteria (SFB) proved to be an excellent indicator of very recent human faecal pollution (hours to days) in the investigated tropical stream and groundwater habitats. SFB were recovered from human faeces and sources potentially contaminated with human excreta. SFB were undetectable in animal faeces and environmental samples not contaminated with human faeces. Microcosm studies demonstrated a rapid die-off rate in groundwater (T90 value 0.6 days) and stream water (T90 value 0.9-1.7 days). Discrimination sensitivity analysis, including E. coli, faecal coliforms, total coliforms and Clostridium perfringens spores, revealed high ability of SFB to distinguish differing levels of faecal pollution especially for streams although high background levels of interfering bacteria can complicate its recovery on the used medium. Due to its faster die-off, as compared to many waterborne pathogens, SFB cannot replace microbiological standard parameters for routine water quality monitoring but it is highly recommendable as a specific and complementary tool when human faecal pollution has to be localized or verified. Because of its exclusive faecal origin and human specificity it seems also worthwhile to include SFB in future risk evaluation studies at tropical water resources in order to evaluate under which situations risks of infection may be indicated.

Determinação dos fatores de recuperação do 111In e do 99mTc na quantificação de atividade com imagens SPECT

OBJETIVO: Determinar, experimentalmente, os coeficientes de recuperação do 111In e do 99mTc usando imagens SPECT. MATERIAIS E MÉTODOS: Quatro diferentes concentrações de 111In e de 99mTc foram usadas para quantificar a atividade em esferas de diferentes tamanhos. As imagens foram obtidas com um equipamento híbrido SPECT/CT, com dois detectores. A reconstrução das imagens foi realizada usando o método iterativo ordered subset expectation maximization (OSEM). A correção de atenuação foi realizada com o uso de um mapa de atenuação e a correção de espalhamento foi realizada usando a técnica das janelas de energia. RESULTADOS: Os resultados mostraram que o efeito do volume parcial foi observado de forma mais significativa para as esferas com volume < 6 ml. Para o 111In, os resultados mostram uma dependência com relação às concentrações usadas nas esferas e ao nível de background usado. Para o 99mTc, pôde-se observar uma tendência à subestimação dos resultados quando os níveis mais altos de background foram utilizados. CONCLUSÃO: É necessário usar os fatores de correção para compensar o efeito do volume parcial em objetos com volume < 6 ml para ambos os radionuclídeos. A subtração das contagens espúrias presentes nas imagens SPECT foi o fator que mais influenciou na quantificação da atividade nessas esferas.

Impacts of point source and diffuse metal and nutrient loading on three northern boreal lakes

A geochemical–paleolimnological study was conducted to investigate human influences on three lakes (Nuasjärvi, Jormasjärvi and Kolmisoppi) located in an area with high background levels of metals and sulphur in bedrock and till overburden. Accordingly, background concentrations of Co, Fe, Mg, Mn, Ni and Zn were above average in sediments of the study lakes. The land use-related erosion and transport of particulate matter into Lake Nuasjärvi started as early as in the seventeenth century, while increased inputs to Lake Jormasjärvi date to the eighteenth century and Lake Kolmisoppi to the 1970s and 1980s. Local tills and fine-grained sediments are the source of the particles and hydraulic sorting has resulted in elevated sediment concentrations of Ca, Cr, Cu, K, Mg, Na and Ni. At the same time, sedimentation of carbon and autochthonous phases has decreased, leading to low concentrations of Co, Fe and Mn in the erosion-associated sediment layers in Nuasjärvi and Kolmisoppi. Despite the geochemical changes, no marked eutrophication of the lakes could be detected with diatom-based nutrient reconstructions during the early land-use period. Elevated amounts of sulphur and chalcophilic elements were deposited throughout the study area during the 1970s and 1980s. In Lake Nuasjärvi combination of the elements is associated with the Lahnaslampi mine and the difference in the sulphide degradation rate is reflected as a sequence of element mobility and sedimentation in the order 1) S, and 2) Co, Ni, Cu, Zn, Cd and Sb. Sulphur, Cu, Ni, Pb and Zn enrichment in the other two lakes is related to other land uses and to atmospheric deposition. In addition to sulphur and metals, these most recent inputs from the catchment have caused nutrient enrichment in all three study lakes, most notably in the lowest-lying Lake Nuasjärvi. This lake has the highest percentage of fine-grained soils in its catchment and also suffers from point source nutrient inputs. In addition, metals (Ni) had a signal in diatom assemblages in Lake Nuasjärvi that was statistically independent of eutrophication (N:C) but inseparable from mineral matter inputs (K).

Multicenter Comparison of Two Norovirus ORF2-Based Genotyping Protocols

Point source norovirus outbreaks can be difficult to track due to high background levels of the virus in the environment and the limited strain variation in some genotyping regions. However, rapid and accurate source identification can limit the spread of a foodborne outbreak and reduce the number of cases. Harmonization of genotyping assays is critical for enabling the rapid exchange of sequence data nationally and internationally. Several regions of the genome have been proposed for this purpose, but no consensus has been reached. In the present study, two standardized genotyping protocols (region C and region D) were evaluated by nine laboratories in Canada and the United States, using a coded panel of 96 fecal specimens representing 22 different norovirus genotypes. Overall, region C typing had a success rate of 78% compared to 52% for region D; however, region D provides greater nucleotide sequence diversity for identifying new GII.4 variant strains. Significant differences in the genotyping success rate were observed among the nine participating laboratories (10% to 100%) and among the different genotypes (6% to 100%). For several genogroup II strains, reduced region D amplification correlated directly with mismatches between primer sequences and the template. Based on overall performance, we recommend the region C protocol for routine genotyping of noroviruses, while the region D protocol may be useful for identifying new GII.4 variants. Standardized genotyping protocols will enable rapid exchange of outbreak and sequence data through electronic norovirus surveillance networks.

Molecular Tools and the Biology of Low-dose Effects

Most environmental protection issues concern the often chronic exposure of large populations to low doses of chemical toxins and ionizing radiation. However, measuring the effects of low doses on populations exposed over long time periods is highly problematic. Politically driven opinions often tend to take the place of science. Part of the problem is that epidemiology is a weak tool when the level of exposure is low. High background levels of exposure, genetic diversity, and exposure uncertainties all contribute to “noise” and make dose-response relationships difficult to define. Uncertainty feeds anxiety, leading to polarized politics. This review looks at the promise of molecular technologies for identifying the effects of low doses of radiation and identifies some of the issues involved in defining risk after low-dose exposures. While the main pollutant discussed in this article is ionizing radiation, the analysis could apply equally well to other toxic exposures or to combined radiation and chemical ...

Crystalline structure of the Au(1 1 1) surface revealed by stereographic intensity DEPES maps

The intensity of elastically backscattered electrons at the primary electron beam energy 1.9 keV was used to obtain a stereographic map of Au(1 1 1) by means of the directional elastic peak electron spectroscopy (DEPES). An experimental result is compared with the theoretical data obtained by using multiple scattering calculations (MS) performed for both not-reconstructed and model-reconstructed clusters. The lateral lattice misfit of the first layer leads to quantitative changes of theoretical intensities showing a sensitivity of DEPES to the short atomic chain axial order. This comparison proves that a main contribution of the experimental contrast originates from a higher background level. Moreover an anisotropy of the inelastic mean free path is discussed in the paper.