181 research outputs found
A Study on the Analytical Sensitivity of 6 BSE Tests Used by the Canadian BSE Reference Laboratory
Bovine spongiform encephalopathy (BSE) surveillance programs
have been employed in numerous countries to monitor BSE prevalence and to
protect animal and human health. Since 1999, the European Commission (EC)
authorized the evaluation and approval of 20 molecular based tests for the rapid
detection of the pathological prion protein (PrPsc) in BSE infection.
The diagnostic sensitivity, convenience, and speed of these tests have made
molecular diagnostics the preferred method for BSE surveillance. The aim of this
study was to determine the analytical sensitivity of 4 commercially available
BSE rapid-test kits, including the Prionics®-Check WESTERN,
the Prionics® Check-PrioSTRIP™, the
BioRad® TeSeE™ ELISA, and the IDEXX®
HerdChek™ EIA. Performances of these tests were then compared
to 2 confirmatory tests, including the BioRad® TeSeE™
Western Blot and the modified Scrapie Associated
Fibrils (SAF)/OIE Immunoblot. One
50% w/v homogenate was made from experimentally generated C-type BSE
brain tissues in ddH2O. Homogenates were diluted through a background
of BSE-negative brainstem homogenate. Masses of both positive and negative
tissues in each dilution were calculated to maintain the appropriate tissue
amounts for each test platform. Specific concentrated homogenization buffer was
added accordingly to maintain the correct buffer condition for each test.
ELISA-based tests were evaluated using their respective software/detection
platforms. Blot-protocols were evaluated by manual measurements of blot signal
density. Detection limitations were determined by fitted curves intersecting the
manufacturers' positive/negative criteria. The confirmatory SAF Immunoblot
displayed the highest analytical sensitivity, followed by the IDEXX®
HerdChek™ EIA, Bio-Rad®
TeSeE™ Western Blot, the Bio-Rad®
TeSeE™ ELISA, Prionics®-Check
PrioSTRIP™, and Prionics®-Check
WESTERN™, respectively. Although the tests performed at different
levels of sensitivity, the most sensitive and least sensitive of the rapid tests
were separated by 2 logs in analytical sensitivity, meeting European performance
requirements. All rapid tests appear suitable for targeted BSE surveillance
programs, as implemented in Canada
Person-to-Person Transmission of Nipah Virus in a Bangladeshi Community
Transmission of this virus highlights the need for infection control strategies for resource-poor settings
Association of a Bovine Prion Gene Haplotype with Atypical BSE
Background: Atypical bovine spongiform encephalopathies (BSEs) are recently recognized prion diseases of cattle. Atypical BSEs are rare; approximately 30 cases have been identified worldwide. We tested prion gene (PRNP) haplotypes for an association with atypical BSE.
Methodology/Principle Findings: Haplotype tagging polymorphisms that characterize PRNP haplotypes from the promoter region through the three prime untranslated region of exon 3 (25.2 kb) were used to determine PRNP haplotypes of six available atypical BSE cases from Canada, France and the United States. One or two copies of a distinct PRNP haplotype were identified in five of the six cases (p = 1.36×10-4, two-tailed Fisher’s exact test; CI95% 0.263–0.901, difference between proportions). The haplotype spans a portion of PRNP that includes part of intron 2, the entire coding region of exon 3 and part of the three prime untranslated region of exon 3 (13 kb).
Conclusions/Significance: This result suggests that a genetic determinant in or near PRNP may influence susceptibility of cattle to atypical BSE
An ultrasoft X-ray multi-microbeam irradiation system for studies of DNA damage responses by fixed- and live-cell fluorescence microscopy
Localized induction of DNA damage is a valuable tool for studying cellular DNA damage responses. In recent decades, methods have been developed to generate DNA damage using radiation of various types, including photons and charged particles. Here we describe a simple ultrasoft X-ray multi-microbeam system for high dose-rate, localized induction of DNA strand breaks in cells at spatially and geometrically adjustable sites. Our system can be combined with fixed- and live-cell microscopy to study responses of cells to DNA damage
Fluorescence spectrum of a two-level atom driven by a multiple modulated field
We investigate the fluorescence spectrum of a two-level atom driven by a multiple amplitude-modulated field. The driving held is modeled as a polychromatic field composed of a strong central (resonant) component and a large number of symmetrically detuned sideband fields displaced from the central component by integer multiples of a constant detuning. Spectra obtained here differ qualitatively from those observed for a single pair of modulating fields [B. Blind, P.R. Fontana, and P. Thomann, J. Phys. B 13, 2717 (1980)]. In the case of a small number of the modulating fields, a multipeaked spectrum is obtained with the spectral features located at fixed frequencies that are independent of the number of modulating fields and their Rabi frequencies. As the number of the modulating fields increases, the spectrum ultimately evolves to the well-known Mellow triplet with the sidebands shifted from the central component by an effective Rabi frequency whose magnitude depends on the initial relative phases of the components of the driving held. For equal relative phases, the effective Rabi frequency of the driving field can be reduced to zero resulting in the disappearance of fluorescence spectrum, i.e., the atom can stop interacting with the field. When the central component and the modulating fields are 180 degrees out of phase, the spectrum retains its triplet structure with the sidebands located at frequencies equal to the sum of the Rabi frequencies of the component of the driving field. Moreover, we shaw that the frequency of spontaneous emission can be controlled and switched from one frequency to another when the Rabi frequency or initial phase of the modulating fields are varied
Commercial Arctic shipping through the Northeast Passage:routes, resources, governance, technology, and infrastructure
The Russian and Norwegian Arctic are gaining notoriety as an alternative maritime route connecting the Atlantic and Pacific Oceans and as sources of natural resources. The renewed interest in the Northeast Passage or the Northern Sea Route is fueled by a recession of Arctic sea ice coupled with the discovery of new natural resources at a time when emerging and global markets are in growing demand for them. Driven by the expectation of potential future economic importance of the region, political interest and governance has been rapidly developing, mostly within the Arctic Council. However, this paper argues that optimism regarding the potential of Arctic routes as an alternative to the Suez Canal is overstated. The route involves many challenges: jurisdictional disputes create political uncertainties; shallow waters limit ship size; lack of modern deepwater ports and search and rescue (SAR) capabilities requires ships to have higher standards of autonomy and safety; harsh weather conditions and free-floating ice make navigation more difficult and schedules more variable; and more expensive ship construction and operation costs lessen the economic viability of the route. Technological advances and infrastructure investments may ameliorate navigational challenges, enabling increased shipping of natural resources from the Arctic to global markets.Albert Buixadé Farré, Scott R. Stephenson, Linling Chen, Michael Czub, Ying Dai, Denis Demchev, Yaroslav Efimov, Piotr Graczyk, Henrik Grythe, Kathrin Keil, Niku Kivekäs, Naresh Kumar, Nengye Liu, Igor Matelenok, Mari Myksvoll, Derek O'Leary, Julia Olsen, Sachin Pavithran.A.P., Edward Petersen, Andreas Raspotnik, Ivan Ryzhov, Jan Solski, Lingling Suo, Caroline Troein, Vilena Valeeva, Jaap van Rijckevorsel and Jonathan Wightin
Cholesterol Induces Specific Spatial and Orientational Order in Cholesterol/Phospholipid Membranes
In lipid bilayers, cholesterol facilitates the formation of the liquid-ordered phase and enables the formation of laterally ordered structures such as lipid rafts. While these domains have an important role in a variety of cellular processes, the precise atomic-level mechanisms responsible for cholesterol's specific ordering and packing capability have remained unresolved
Cholesterol Induces Specific Spatial and Orientational Order in Cholesterol/Phospholipid Membranes
In lipid bilayers, cholesterol facilitates the formation of the liquid-ordered phase and enables the formation of laterally ordered structures such as lipid rafts. While these domains have an important role in a variety of cellular processes, the precise atomic-level mechanisms responsible for cholesterol's specific ordering and packing capability have remained unresolved
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