bluuebunny/crossref_metadata_2025 huggingface dataset:
Capacitance measurements on small parallel plate capacitors using nanoscale impedance microscopy
Authors: Schneegans Olivier , Chrétien Pascal , Houzé Frédéric , Meyer René
Published: January 2007

Capacitance values in the picofarad to femtofarad range have been measured on a set of square parallel plate capacitors using a homemade nanoscale impedance microscopy (NIM) device and compared with numerical simulations. A simple analytical model involving the main geometrical parameters is proposed, which correctly fits the experimental results. This model was validated by further measurements on rectangular electrodes and capacitors surrounded by guard rings. The edge effects and stray capacitance contribution were hence determined. Finally, the present resolution of our NIM device was estimated by imaging a tiny 8×8μm2 capacitor, confirming the relevance of such reference samples.
Terahertz quantum-cascade lasers based on a three-well active module
Authors: Luo H. , Laframboise S. R. , Wasilewski Z. R. , Aers G. C. , Liu H. C. , Cao J. C.
Published: January 2007

The authors report on a design of terahertz quantum-cascade lasers based on three-well active modules. Each module consists of two tunnel-coupled wells for the two lasing states and another well for both resonant-phonon depopulation and carrier injection. This design is the simplest so far among the various published working devices. The test device has a lasing frequency of 3.4THz and maximum operating temperature of 142K.
Activation-induced cytidine deaminase (AID) promotes B cell lymphomagenesis in Emu-cmyc transgenic mice
Authors: Kotani Ai , Kakazu Naoki , Tsuruyama Tatsuaki , Okazaki Il-mi , Muramatsu Masamichi , Kinoshita Kazuo , Nagaoka Hitoshi , Yabe Daisuke , Honjo Tasuku
Published: January 2007

Activation-induced cytidine deaminase (AID), which is essential to both class switch recombination and somatic hypermutation of the Ig gene, is expressed in many types of human B cell lymphoma/leukemia. AID is a potent mutator because it is involved in DNA breakage not only of Ig but also of other genes, including proto-oncogenes. Recent studies suggest that AID is required for chromosomal translocation involving cmyc and Ig loci. However, it is unclear whether AID plays other roles in tumorigenesis. We examined the effect of AID deficiency on the generation of surface Ig-positive B cell lymphomas in Emu-cmyc transgenic mice. Almost all lymphomas that developed in AID-deficient transgenic mice were pre-B cell lymphomas, whereas control transgenic mice had predominantly B cell lymphomas, indicating that AID is required for development of B but not pre-B cell lymphomas from cmyc overexpressing tumor progenitors. Thus, AID may play multiple roles in B cell lymphomagenesis.
Farmer decisions to adopt genetically modified crops.
Authors: Alexander C.
Published: January 2007

This article reviews the literature on farmer decision-making related to genetically modified (GM) crops. The literature based on farmer surveys, linear programming models and yield trials clearly shows that the adoption of GM crops benefits many farmers, but not all and that these benefits depend on the specific characteristics of the producer and the operation. Research on farmer adoption of GM crops provides insight into the interaction between farmers human capital, information and their risk preferences. As new GM crops are introduced or receive approval for planting, research will continue to be needed to understand which farmers will benefit.
Mycoplasma hyopneumoniae-induced disease.
Authors: Thacker E.
Published: January 2007

Respiratory disease remains a significant problem to the swine industry. In most production systems, multiple pathogens and their interactions are responsible for the pneumonia and reduced productivity that are observed.
Mycoplasma hyopneumoniae
, the cause of enzootic pneumonia, remains an important contributor to respiratory disease in swine herds throughout the world. Recent research has demonstrated that different isolates of
M. hyopneumoniae
exhibit varied degrees of virulence and can complicate diagnostics. Diagnostics associated with
M. hyopneumoniae
can be frustrating due to the chronic nature of the organism and its location within the airways of infected pigs.
M. hyopneumoniae
is also problematic to the swine industry because of its impact on disease caused by other pathogens such as porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2). Vaccination remains the primary method of control, although judicial use of antibiotics can help reduce disease. Controlling
M. hyopneumoniae
-induced disease is an important strategy for increased productivity and improved respiratory health in most herds and is economically justified in most herds.
Agricultural systems: sensitivity to climate change.
Authors: Fuhrer J.
Published: January 2007

Agriculture is among the sectors most directly exposed to climate variability and change, with consequences for food production and food security. This paper aims to review the most recent literature on the sensitivity to climate change of agricultural systems by considering four hierarchical levels: (i) crops and grasslands, (ii) cropping systems, (iii) livestock systems, and (iv) farming systems. The available information suggests that a significant rise in mean temperature is likely to reduce crop yields in many areas, with the most threatened systems located in areas with decreasing rainfall. In cooler regions, more favourable mean temperatures and the extension of the growing season may stimulate potential productivity. More frequent dry spells in a warmer climate are likely to increase the risk of crop failure, unless irrigation can be expanded and be combined with improved water retention and water yield. In grasslands, the sensitivity may be larger in extensively than in intensively managed systems because of the lack of adaptive management interventions. Finally, climate change could seriously alter the productivity of animal systems, both through direct effects on the animal well-being and indirect effects via diet quality and forage availability. Overall, there is ample evidence that agricultural systems are sensitive to climate change, and that effects on potential productivity ranges from being extremely negative in already water-limited areas to more favourable in currently temperature-limited regions.
Diagnosis and control of heartwater,
Ehrlichia ruminantium
, infection: an update.
Authors: Mahan S. M.
Published: January 2007

Heartwater, an acute and fatal tick-transmitted disease of domestic and wild ruminants caused by a rickettsial agent
Ehrlichia ruminantium
, continues to negatively impact animal health and production in sub-Saharan Africa. Its control is hampered by the absence of safe and effective vaccines. Over the last two decades in particular, major advances have occurred facilitating a better understanding of its epidemiology, vector biology and dynamics of transmission, pathogen propagation and characterization, molecular biology, antigenic repertoire and immunity. This research has facilitated development of improved diagnostic assays and strategically influenced research on development of efficacious vaccines. Heartwater serology is constrained by the detection of antigenic cross-reactions with genetically related ehrlichial agents. Serology therefore is not a reliable method for diagnosis of heartwater or for predicting its distribution or spread. Polymerase chain reaction (PCR)-based detection, especially targeting the sequences of the pCS20 gene fragment of
E. ruminantium
, is reliable and has been determined to be the most specific method for pathogen detection and hence disease surveillance. The pCS20 PCR assay readily detects infected ticks and clinically ill animals but does not always detect carrier animals. The reason for this observation will be discussed. Research on improved vaccines has focused on development of attenuated, inactivated and recombinant vaccines for heartwater. This research has led to the field evaluation of an inactivated vaccine which has provided the proof of concept for the development of recombinant vaccines for heartwater. The inactivated vaccine protects cattle, sheep and goats against natural field tick challenge, but these trials have highlighted that
E. ruminantium
antigenic disparity will be an important factor affecting vaccine deployment in the field. Progress in recombinant vaccine research has led to preliminary testing of some E. ruminantium antigens delivered as DNA vaccines. The recent publication of the genome sequence of two strains of
E. ruminantium
is likely to expedite the development of recombinant vaccines for heartwater, especially through reverse vaccinology, which has been used to successfully identify protective antigens of various other pathogens.
Chemical alternatives to methyl bromide for vegetable crop production in Florida, United States.
Authors: Santos B. M. , Gilreath J. P.
Published: January 2007

Vegetable crop production in Florida, USA, relies on planting on polyethylene-mulched beds fumigated with methyl bromide plus chloropicrin (MBr+Pic) for soil-borne disease, nematode and weed control. However, MBr for agricultural use has been phased out because it is an ozonedepleting molecule. A considerable amount of research has been conducted to identify alternatives to MBr in Florida, where most of the year soil-borne pests thrive under its subtropical climate. Most of the published articles have studied the efficacy of 1,3-dichloropropene (1,3-D), Pic, dazomet and metam on soil-borne pests. Also, there are preliminary results with methyl iodide, propylene oxide and dimethyl disulfide, which currently are still the subject of scrutiny. Reported studies have shown that there is no definitive one-to-one replacement to this fumigant for controlling soil-borne disease, nematodes and weeds. Instead, pest management has focused on combining the activity of several active ingredients and improving fumigant retention in the soil with mulches. In particular, the majority of available MBr alternatives provide effective control against most soil-borne diseases and nematodes, assuming that correct application methods and rates are used. However, in situations where
Cyperus
is troublesome, alternative fumigants could be combined with herbicides to minimize weed interference.
Nearby nature and green areas encourage outdoor activitiesand decrease mental stress.
Authors: Nielsen T. S. , Hansen K. B.
Published: January 2007

The article presents the results from a Danish representative study of the use of green areas; the importance of access; and the effect of access to green areas, as well as use frequency, on mental stress. Results indicate that the users of green areas are mainly attracted by the possibility of experiencing greenery and nature; that time constraints and climate are major obstacles to the use of green areas; and that ease of access from the home has a substantial impact on use frequencies. The results also indicate that short distances to green areas from the dwelling and high frequency of use for green areas and gardens are related to lower levels of mental stress. The effect of green areas on mental stress has made green space a target and a tool in health policy and urban planning in the City of Copenhagen. Policies will improve access to green areas and increase the attractiveness of the areas with the aim of increasing the use of green areas and the exposure to greenery and it is hoped that this will increase the health standard of the inhabitants of Copenhagen.
Navigating the Water Framework Directive: implications for agriculture and beyond.
Authors: Lago M. , Mouratiadou I. , Moran D.
Published: January 2007

The Water Framework Directive (WFD) is a key piece of European environmental legislation introduced in 2000 to deliver on water quality objectives. The Directive introduces a set of principles and measures that rationalize both the supply and the demand for water across member states, with few industries being exempt from its influence. Water is a good with many uses and elements of both public and private ownership. Optimizing its use therefore represents a complex challenge for social planners trading off efficiency and equity dimensions of competing uses of an essentially scarce resource. This paper considers how the Directive introduces economic principles into water use; effectively treating water (quantity and quality) as an economic good rather than a free resource. Focusing predominantly on agriculture, this perspective helps to clarify the nature of all discharge and abstraction uses by the sector and how agricultural uses lead to social tradeoffs with other non-agricultural users. Ultimately, the perspective helps to illuminate how and where water is best employed to maximize its value to society.
Weed control with methyl bromide alternatives.
Authors: Hanson B. D. , Shrestha A.
Published: January 2007

Methyl bromide (MeBr) has been used for several decades for preplant (PRE) soil fumigation in high-value agricultural and horticultural crops because it can provide broad-spectrum control of insects, nematodes, pathogens, and weeds. However, MeBr has been identified as an ozone-depleting chemical and is associated with hazards to human heath, plants, and animals. Therefore, a global agreement to gradually phase-out ozone depleting chemicals was made with the signing of the 'Montreal Protocol' in 1987 and research for effective and sustainable alternatives to MeBr has been a priority since 1995. Several alternative fumigants and non-chemical alternatives for weed control have been tested. In many agricultural systems the phase-out of MeBr presents a critical challenge because alternative pest control measures are ineffective, costly, or pose hazards to the environment and human health. In this paper, we review the status of MeBr alternatives with a focus on weed control in high-value cropping systems. It is concluded that no currently available alternative chemical or management practice has the same broad-spectrum efficacy and consistency as MeBr. Because the development of a single alternative to MeBr is unlikely, weed control in many high-value fruit, vegetable, and ornamental crops will become an even greater challenge in the absence of MeBr. Development of crop- and region-specific integrated pest management systems that include appropriate fumigants, herbicides and cultural practices will be necessary to maintain productivity at levels and prices that meet current grower and consumer expectations.
Amelioration strategies for salinity-induced land degradation.
Authors: Qadir M. , Schubert S. , Noble A. D. , Saqib M. , Saifullah Saifullah
Published: January 2007

Salinization of soils is a major impediment to their optimal utilization in many arid and semi-arid regions throughout the world. In several large irrigation schemes, salinity-induced land degradation has increased steadily over the last few decades with concurrent reductions in agricultural productivity and sustainability. Currently, saline soils occur within at least 100 countries. These soils need explicit approaches in their amelioration since soil salinization cannot be reduced by routine irrigation and crop management practices. The approaches used to ameliorate saline soils can be broadly divided into four major categories: (1) leaching of bare saline soils to move excess soluble salts from upper to lower soil depths or out of soil profile in the presence of a natural or artificial drainage system; (2) leaching of cropped saline soils with certain plant species, which can withstand ambient salinity levels; (3) surface flushing or mechanical removal of salts from soils that contain salt crusts at the surface or where drainage is inadequate and leaching is restricted by the presence of a shallow water table or highly impermeable profile; and (4) reduction of salts from saline soils through biological means - the harvest and removal of high-salt accumulating aerial plant parts - in areas with negligible irrigation water or rainfall for leaching. Research and practice have shown that in the presence of a drainage system, saline soils can be brought back to a highly productive state by leaching the excess soluble salts from the effective rooting depth. Among the amelioration methods, cropping in conjunction with leaching has an advantage; cropping during or between leaching events increases salt removal efficiency because of a decrease in soil-water content under unsaturated water flow conditions with a concurrent decrease in large pore bypass and drainage volume. However, anaerobic conditions in soil may occur during leaching of cropped soils, thereby affecting growth of those plant species that are sensitive to such conditions. Thus, in addition to existing salt-resistant plant species, research is needed to explore or develop genotypes that can withstand the twin stresses of salinity and hypoxia. Although significant efforts have been made to develop models for simulating movement and reactions of salts in saline soils during the amelioration process, these models need evaluation and verification under actual field conditions.
Involvement of a Golgi-resident GPI-anchored Protein in Maintenance of the Golgi Structure
Authors: Li Xueyi , Kaloyanova Dora , van Eijk Martin , Eerland Ruud , van der Goot Gisou , Oorschot Viola , Klumperman Judith , Lottspeich Friedrich , Starkuviene Vytaute , Wieland Felix T. , Helms J. Bernd
Published: January 2007

The Golgi apparatus consists of a series of flattened cisternal membranes that are aligned in parallel to form stacks. Cytosolic-oriented Golgi-associated proteins have been identified that may coordinate or maintain the Golgi architecture. Here, we describe a novel GPI-anchored protein, Golgi-resident GPI-anchored protein (GREG) that has a brefeldin A-sensitive Golgi localization. GREG resides in the Golgi lumen as a cis-oriented homodimer, due to strong interactions between coiled-coil regions in the C termini. Dimerization of GREG as well as its Golgi localization depends on a unique tandem repeat sequence within the coiled-coil region. RNA-mediated interference of GREG expression or expression of GREG mutants reveals an essential role for GREG in maintenance of the Golgi integrity. Under these conditions, secretion of the vesicular stomatitis virus glycoprotein protein as a marker for protein transport along the secretory pathway is inhibited, suggesting a loss of Golgi function as well. These results imply the involvement of a luminal protein in Golgi structure and function.
Phytophthora Root Rot and Stem Canker Found on Nordmann and Subalpine Fir in Norwegian Christmas Tree Plantations
Authors: Talgø Venche , Herrero Maria L. , Toppe Brita , Klemsdal Sonja S. , Stensvand Arne
Published: January 2007

In 2004, Phytophthora symptoms were observed on two different fir species used for Christmas trees in Norway. Isolations resulted in a Phytophthora sp. related to P. inundata from relatively newly established Nordmann fir (Abies nordmanniana) and P. megasperma from seven-year-old subalpine fir (A. lasiocarpa). The Nordmann fir plantation was more severely damaged, with approximately 70% of the trees dead or dying. In the field with subalpine fir, approximately 25% of the trees had yellow or brown foliage and stem canker. Pathogenicity was proven for both Phytophthora isolates on seedlings from their respective host plants. The massive infestation in the Nordmann fir plantation approximately one year after planting suggests that the pathogen was introduced into the planting with the transplants. Except for a recent report of P. cambivora on noble fir (A. procera) produced for bough production (17), Phytophthora has never been reported before on fir in Norway.

Accepted for publication 2 October 2006. Published 19 January 2007.
Clinical, neuropathological and immunohistochemical features of sporadic and variant forms of Creutzfeldt–Jakob disease in the squirrel monkey (Saimiri sciureus)
Authors: Williams Lawrence , Brown Paul , Ironside James , Gibson Susan , Will Robert , Ritchie Diane , Kreil Thomas R. , Abee Christian
Published: January 2007

The squirrel monkey (Saimiri sciureus) has been shown to be nearly as susceptible as the chimpanzee to experimentally induced Creutzfeldt–Jakob disease (CJD), and has been used extensively in diagnostic and pathogenetic studies. However, no information is available concerning the clinicopathological characteristics of different strains of human transmissible spongiform encephalopathy (TSE) in this species, in particular, strains of sporadic and variant CJD (sCJD and vCJD, respectively). Brain homogenates from patients with sCJD or vCJD were inoculated intracerebrally at dilutions of 10−1 or 10−3 into the left frontal cortex of squirrel monkeys. Animals were kept under continuous clinical surveillance during the preclinical and clinical phases of disease, and regularly underwent standardized behavioural testing. Brains from three animals in the sCJD and vCJD groups were examined histopathologically and immunohistochemically for the presence of pathognomonic misfolded protein (PrPTSE). Overall, incubation periods and durations of illness were slightly shorter in monkeys infected with sCJD than in those infected with vCJD, but the earliest signs of illness (ataxia and tremors) were the same in both groups. Clinical disease in the sCJD monkeys was somewhat more severe and of shorter duration. Post-mortem examinations revealed distinctive patterns of spongiform change and PrPTSE distribution in the brains of sCJD and vCJD animals, similar to those seen in humans except that amyloid plaques were not present. PrPTSE was uniformly absent from peripheral lymphoid tissues in both groups of animals. Human strains of sCJD and vCJD cause distinguishable clinicopathological features in the squirrel monkey that can provide a baseline for the evaluation of future therapeutic studies.
Systemic immune response after rotavirus inoculation of neonatal mice depends on source and level of purification of the virus: implications for the use of heterologous vaccine candidates
Authors: Reimerink Johan H. J. , Boshuizen Jos A. , Einerhand Alexandra W. C. , Duizer Erwin , van Amerongen Geert , Schmidt Nico , Koopmans Marion P. G.
Published: January 2007

Rotavirus is an important cause of morbidity and mortality worldwide and vaccines are currently under development, with clinical trails conducted in humans worldwide. The immune responses in infant BALB/c mice were examined following oral inoculation with murine rotavirus EDIM (2×104 focus-forming units) and with three CsCl gradient-purified fractions of heterologous simian rotavirus SA11 (standardized at 2×106 CCID50) that differed in antigen composition: fraction 1 was enriched for double-layered rotavirus particles, fraction 2 for triple-layered particles and fraction 3 consisted mainly of cell components. Diarrhoea and high IgG responses, but marginal IgA responses, were observed after inoculation with all three SA11 fractions. Virus shedding was observed in all EDIM-inoculated mice, but in none of the SA11-inoculated mice. Rotavirus-specific IgG1 : 2a ratios were similar in mice inoculated with EDIM and SA11 fraction 1, but higher for SA11 fraction 3- and lower for SA11 fraction 2-inoculated mice. A higher IgG1 : 2a ratio indicates a more Th2-like immune response. This undesirable response is apparently mostly induced by inoculation with heterologous rotavirus in the presence of abundant cell-associated and soluble rotavirus proteins, compared with infection with a more purified preparation or with homologous virus. These data show that, following inoculation with a standardized amount of infectious virus, the composition of the fraction influences the outcome of the immune responses significantly.
Efficient dissemination of prions through preferential transmission to nearby cells
Authors: Paquet Sophie , Langevin Christelle , Chapuis Jérome , Jackson Graham S. , Laude Hubert , Vilette Didier
Published: January 2007

Despite circumstantial evidence that prions can be found extracellularly or at the surface of infected cells, little is known about how these infectious agents spread from cell to cell. In order to gain better insight into this critical issue, this study used two different cell lines (neuroglial MovS and epithelial Rov cells) that have previously been shown to be permissive for ovine prion multiplication. Co-culture of infected cells and uninfected target cells at a ratio of 1 : 9 resulted in total infection of MovS cells within 10 days but not of Rov cell cultures, suggesting that the efficiency of prion dissemination may vary greatly depending on the type of permissive cell. Analysis of the spatial distribution of the newly infected cells revealed that, although long-range spread could also occur, cells proximal to the infected donor cells consistently accumulated more abnormal PrP, consistent with preferential infection of nearby cells. This experimental approach, focused on dissemination among living cells, could help in the analysis of mechanisms involved in the cell-to-cell spread of prion infections.
Cross-genotype characterization of genetic diversity and molecular adaptation in hepatitis C virus envelope glycoprotein genes
Authors: Brown Richard J. P. , Tarr Alexander W. , McClure C. Patrick , Juttla Vicky S. , Tagiuri Nader , Irving William L. , Ball Jonathan K.
Published: January 2007

Investigation of the mechanisms underlying hepatitis C virus (HCV) envelope glycoprotein gene evolution will greatly assist rational development of broadly neutralizing antibody-based vaccines or vaccine components. Previously, comprehensive cross-genotype evolutionary studies of E1E2 have not been possible due to the paucity of full-length envelope gene sequences representative of all major HCV genotypes (1–6) deposited in international sequence databases. To address this shortfall, a full-length E1E2 clone panel, corresponding to genotypes of HCV that were previously under-represented, was generated. This panel, coupled with divergent isolates available via international sequence databases, was subjected to high-resolution methods for determining codon-substitution patterns, enabling a fine-scale dissection of the selective pressures operating on HCV E1E2. Whilst no evidence for positive selection was observed in E1, the E2 protein contained a number of sites under strong positive selection. A high proportion of these sites were located within the first hypervariable region (HVR1), and statistical analysis revealed that cross-genotype adaptive mutations were restricted to a subset of homologous positions within this region. Importantly, downstream of HVR1, a differential genotype-specific distribution of adaptive mutations was observed, suggesting that subtly different evolutionary pressures shape present-day genotype diversity in E2 outside HVR1. Despite these observations, it is demonstrated that purifying selection due to functional constraint is the major evolutionary force acting on HCV E1E2. These findings are important in the context of neutralizing-antibody vaccine targeting, as well as in contributing to our understanding of E1E2 function.
Mapping of a self-interaction domain of the cytomegalovirus protein kinase pUL97
Authors: Schregel Vera , Auerochs Sabrina , Jochmann Ramona , Maurer Katja , Stamminger Thomas , Marschall Manfred
Published: January 2007

The human cytomegalovirus-encoded protein kinase pUL97 is a determinant of efficient virus replication and fulfils several regulatory functions. In particular, pUL97 interacts with and phosphorylates viral and cellular proteins. Substrate phosphorylation has regulatory consequences on viral replicative stages such as DNA synthesis, transcription and nuclear capsid egress. pUL97, in accordance with related herpesviral protein kinases, possesses strong autophosphorylation activity. Here, we demonstrate that pUL97 shows a pronounced potential to self-interact. Self-interaction of pUL97 is not dependent on its kinase activity, as seen with a catalytically inactive point mutant. The property of self-interaction maps to the amino acid region 231–280 which is separable from the postulated kinase domain. The detection of high-molecular-mass complexes of pUL97 suggests the formation of dimers and oligomers. Importantly, the analysis of pUL97 mutants by in vitro kinase assays demonstrated a correlation between self-interaction and protein kinase activity, i.e. all mutants lacking the ability to self-interact were negative or reduced in their kinase activity. Thus, our findings provide novel insights into the pUL97 structure–activity relationship suggesting an importance of self-interaction for pUL97 functionality.
Genome organization of the Chelonus inanitus polydnavirus: excision sites, spacers and abundance of proviral and excised segments
Authors: Annaheim Marc , Lanzrein Beatrice
Published: January 2007

Polydnaviruses are only found in symbiotic association with parasitic wasps within the families Ichneumonidae and Braconidae (ichnoviruses and bracoviruses). They have a segmented genome consisting of circular double-stranded DNA. In the proviral linear form they are integrated in the wasp's genome; in two bracoviruses, segments were found to be clustered. Proviral segments have direct terminal repeats. Segment excision has been proposed to occur through juxtaposition of these repeats by formation of a loop and recombination; one copy of the repeat then ends up in the circular segment and one in the rejoined DNA. Here we analysed the excision/circularization site of four segments of theChelonus inanitusbracovirus (CiV) and found that they are similar to the two already known sites; on the basis of the combined data an extended excision site motif was found. Analyses of segment flanking sequences led to the first identification of one complete and several partial spacers between proviral segments in a polydnavirus. The spacer between the proviral segments CiV14 and CiV22.5 has a length of 2065 bp; the terminal repeats of CiV14 and CiV22.5 were seen to have an opposite orientation and from this a model on the spacial organization of the loops of the proviral cluster is proposed. Through various approaches it was shown that spacers are not excised or injected into the host. Measurement of relative abundances of various segments in proviral and excised form indicates for the first time that abundant segments are present in multiple copies in the proviral form.
Adaptation of an H7N7 equine influenza A virus in mice
Authors: Shinya Kyoko , Watanabe Shinji , Ito Toshihiro , Kasai Noriyuki , Kawaoka Yoshihiro
Published: January 2007

Wild waterfowl are a reservoir for influenza A viruses, which can be transmitted from these birds to other animal species. Occasionally, influenza A viruses are transmitted to other animal species from animals other than wild waterfowl, e.g. an equine influenza virus has been transmitted to dogs and caused outbreaks. To understand the molecular mechanism by which influenza A viruses adapt to a new animal species, the molecular changes involved in the adaptation of an H7N7 equine influenza A virus were studied in mice. Mutations in the mouse-adapted virus mapped to one amino acid change in the PA protein, one in PB2 and two in PB1. Of these mutations, the Glu-to-Lys substitution at position 627 of PB2 (PB2-E627K) increased virulence appreciably. To understand the mechanism of this increased virulence, a recombinant virus expressing a reporter green fluorescent protein was constructed, thus enabling the effect of this mutation on viral protein expression to be tested in the context of virus replication in situ. It was found that the PB2-E627K substitution in this equine virus contributed to increased viral protein expression and virus replication in mouse cells and enhanced brain invasiveness in mice. These results demonstrate that the importance of the PB2-E627K substitution for mouse adaptation, which was identified previously in human H5N1 isolates, extends to equine influenza A virus.
Comparative titration of experimental ovine BSE infectivity in sheep and mice
Authors: González Lorenzo , Chianini Francesca , Martin Stuart , Sisó Sílvia , Gibbard Louise , Reid Hugh W. , Jeffrey Martin
Published: January 2007

Titration studies of the infectivity of experimental bovine spongiform encephalopathy (BSE) in sheep are necessary to assess the risk for human health posed by the ovine infection relative to the original cattle disease. Here, a comparative titration was performed of sheep-passaged BSE infectivity in Romney sheep and RIII mice, by the intracerebral (i.c.) and i.c. plus intraperitoneal (i.p.) routes, respectively. The sheep-to-mouse species barrier was lower than anticipated, as similar titres were obtained for both sheep [1×105.4 (i.c.) ID50 g−1)] and mice [1×105.0 (i.c.+i.p.) ID50 g−1]. Moreover, sheep of the ARR/ARR PrP genotype all succumbed to i.c. challenge with a 10−3 dilution of 0.5 g of a brainstem pool from BSE-affected sheep, indicating that resistance to natural infection in sheep of this genotype must reside in some mechanism of peripheral pathogenesis.
Inhibition of henipavirus infection by Nipah virus attachment glycoprotein occurs without cell-surface downregulation of ephrin-B2 or ephrin-B3
Authors: Sawatsky Bevan , Grolla Allen , Kuzenko Nina , Weingartl Hana , Czub Markus
Published: January 2007

Nipah virus (NiV) and Hendra virus (HeV) are newly identified members of the family Paramyxoviridae and have been classified in the new genus Henipavirus based on unique genetic characteristics distinct from other paramyxoviruses. Transgenic cell lines were generated that expressed either the attachment protein (G) or the fusion protein (F) of NiV. Functional expression of NiV F and G was verified by complementation with the corresponding glycoprotein, which resulted in the development of syncytia. When exposed to NiV and HeV, expression of NiV G in Crandall feline kidney cells resulted in a qualitative inhibition of both cytopathic effect (CPE) and cell death by both viruses. RT-PCR analysis of surviving exposed cells showed a complete absence of viral positive-sense mRNA and genomic negative-sense viral RNA. Cells expressing NiV G were also unable to fuse with cells co-expressing NiV F and G in a fluorescent fusion inhibition assay. Cell-surface staining for the cellular receptors for NiV and HeV (ephrin-B2 and ephrin-B3) indicated that they were located on the surface of cells, regardless of NiV G expression or infection by NiV. These results indicated that viral interference can be established for henipaviruses and requires only the expression of the attachment protein, G. Furthermore, it was found that this interference probably occurs at the level of virus entry, as fusion was not observed in cells expressing NiV G. Finally, expression of NiV G by either transient transfection or NiV infection did not alter the cell-surface levels of the two known viral receptors.
Differential infection efficiencies of peripheral lung and tracheal tissues in sheep infected with Visna/maedi virus via the respiratory tract
Authors: McNeilly Tom N. , Tennant Peter , Luján Lluís , Pérez Marta , Harkiss Gordon D.
Published: January 2007

The main routes of transmission of Visna/maedi virus (VMV), an ovine lentivirus, are thought to be through ingestion of infected colostrum and/or milk or through inhalation of respiratory secretions. Whereas oral transmission appears to be mediated via epithelial cells within the small intestine, the mechanism of virus uptake in the respiratory tract is unknown. In addition, it is not known whether infection is mediated by cell-associated or cell-free VMV, previous studies having not addressed this question. Intratracheal (i.t.) injection of VMV is known to be a highly efficient method of experimental infection, requiring as little as 101 TCID50 VMV for successful infection. However, using a tracheal organ culture system, we show here that ovine tracheal mucosa is relatively resistant to VMV, with detectable infection only seen after incubation with high titres of virus (⩾105 TCID50 ml−1). We also demonstrate that i.t. injection results in exposure of both trachea and the lower lung and that the time taken for viraemia and seroconversion to occur after lower lung instillation of VMV was significantly shorter than that observed for tracheal instillation of an identical titre of virus (P=0.030). This indicates that lower lung and not the trachea is a highly efficient site for VMV entry in vivo. Furthermore, cell-free virus was identified within the lung-lining fluid of naturally infected sheep for the first time. Together, these results suggest that respiratory transmission of VMV is mediated by inhalation of aerosols containing free VMV, with subsequent virus uptake in the lower lung.
Pregnancy increases the risk of mortality in West Nile virus-infected mice
Authors: Córdoba Laura , Escribano-Romero Estela , Garmendia Antonio , Saiz Juan-Carlos
Published: January 2007

West Nile fever outbreaks in the USA have caused over 700 human deaths, primarily due to neurological disease. The usual transmission route of West Nile virus (WNV) involves mosquito bites; however, alternative routes, including intrauterine infection, have also been reported. Here, the pathogenicity of WNV in mice during gestation has been investigated. An extremely high mortality rate was observed in pregnant mice (98 %, 60/61) compared with non-pregnant mice (52 %, 28/53; P<0.001), independent of the infecting dose or the week of pregnancy. Antibody titres were similar between pregnant and non-pregnant mice and between surviving and non-surviving animals. WNV RNA titres in brains were also similar between pregnant and non-pregnant mice. WNV RNA could be detected in placentas and fetuses. These observations suggest strongly that, in the mouse model, pregnancy increases the risk of severe WNV infection and may help to understand the pathogenic mechanisms involved in WNV infection during pregnancy.
Aptamers in the virologists' toolkit
Authors: James William
Published: January 2007

Aptamers are artificial nucleic acid ligands that can be generatedin vitroagainst a wide range of molecules, including the gene products of viruses. Aptamers are isolated from complex libraries of synthetic nucleic acids by an iterative, cell-free process that involves repetitively reducing the complexity of the library by partitioning on the basis of selective binding to the target molecule, followed by reamplification. For virologists, aptamers have potential uses as tools to help to analyse the molecular biology of virus replication, as a complement to the more familiar monoclonal antibodies. They also have potential applications as diagnostic biosensors and in the development of antiviral agents. In recent years, these two promising avenues have been explored increasingly by virologists; here, the progress that has been made is reviewed.
Ribavirin, human convalescent plasma and anti-β 3 integrin antibody inhibit infection by Sin Nombre virus in the deer mouse model
Authors: Medina Rafael A. , Mirowsky-Garcia Katy , Hutt Julie , Hjelle Brian
Published: January 2007

The New World hantavirusSin Nombre virus(SNV) is an aetiological agent for the often-fatal hantavirus cardiopulmonary syndrome (HCPS). There is no disease model for SNV and specific treatments for HCPS do not exist. By using the deer mouse infectious model, thein vivoinhibitory potential of ribavirin, human anti-SNV immune plasma (HIP), an anti-β3 antibody (ReoPro) and a polyclonal rabbit anti-recombinant nucleocapsid (N) antibody against SNV was investigated. Concurrent intraperitoneal administration of 100 mg ribavirin kg−1prevented seroconversion in all mice at day 15 post-inoculation (p.i.). No evidence of infection was detectable by immunohistochemical staining or by quantitative RT-PCR in two of these six mice. Lower doses of ribavirin, between 5 and 50 mg kg−1, were much less effective at inhibiting infection. Mice given 200 μl aliquots of dilutions as high as 1 : 20 of HIP (neutralizing-antibody titre 800) failed to seroconvert by day 15 p.i. SNV N antigen staining and viral S genome were undetectable in these mice. A subset of mice given higher dilutions of HIP became infected. Treatment with 6 mg ReoPro kg−1did not prevent seroconversion, but was able to reduce viral load. Mice treated with 200 μl anti-N antibody or negative human plasma seroconverted when challenged with SNV, and antigen staining and viral loads were comparable to those seen in untreated controls. These results show that ReoPro can lower viral loads and that ribavirin and HIP, but not anti-N antibody, inhibit seroconversion and reduce viral loads in a dose-dependent manner.
C/EBPβ regulates human immunodeficiency virus 1 gene expression through its association with cdk9
Authors: Mameli Giuseppe , Deshmane Satish L. , Ghafouri Mohammad , Cui Jianqi , Simbiri Kenneth , Khalili Kamel , Mukerjee Ruma , Dolei Antonina , Amini Shohreh , Sawaya Bassel E.
Published: January 2007

Transcriptional regulation of the human immunodeficiency virus type 1 (HIV-1) is a complex event that requires the cooperative action of both viral (e.g. Tat) and cellular (e.g. C/EBPβ, NF-κB) factors. The HIV-1 Tat protein recruits the human positive transcription elongation factor P-TEFb, consisting of cdk9 and cyclin T1, to the HIV-1 transactivation response (TAR) region. In the absence of TAR, Tat activates the HIV-1 long terminal repeat (LTR) through its association with several cellular factors including C/EBPβ. C/EBPβ is a member of the CCAAT/enhancer-binding protein family of transcription factors and has been shown to be a critical transcriptional regulator of HIV-1 LTR. We examined whether Tat–C/EBPβ association requires the presence of the P-TEFb complex. Using immunoprecipitation followed by Western blot, we demonstrated that C/EBPβ–cyclin T1 association requires the presence of cdk9. Further, due to its instability, cdk9 was unable to physically interact with C/EBPβ in the absence of cyclin T1 or Tat. Using kinase assays, we demonstrated that cdk9, but not a cdk9 dominant-negative mutant (cdk9-dn), phosphorylates C/EBPβ. Our functional data show that co-transfection of C/EBPβ and cdk9 leads to an increase in HIV-1 gene expression when compared to C/EBPβ alone. Addition of C/EBP homologous protein (CHOP) inhibits C/EBPβ transcriptional activity in the presence and absence of cdk9 and causes a delay in HIV-1 replication in T-cells. Together, our data suggest that Tat–C/EBPβ association is mediated through cdk9, and that phosphorylated C/EBPβ may influence AIDS progression by increasing expression of HIV-1 genes.
Two SNPs in the SILV gene are associated with silver coat colour in ponies
Authors: Reissmann M. , Bierwolf J. , Brockmann G. A.
Published: January 2007

In horses, a pigment dilution acting only on black eumelanin is the so‐called silver coat colour, which is characterized by a chocolate‐to‐reddish body with a white mane and tail. Using information from other species, we focused our study on SILV as a possible candidate gene for the equine silver phenotype. A 1559‐bp genomic fragment was sequenced in 24 horses, and five SNPs were detected. Two of the five SNPs (DQ665301:g.697A>T and DQ665301:g.1457C>T) were genotyped in 112 horses representing eight colour phenotypes. Both mutations were completely associated with the silver phenotype: all eumelanin‐producing horses (blacks and bays) with atypical white mane and tail were carriers of the [g.697T; g.1457T] haplotype. We identified this haplotype as well as the silver phenotype only in Shetland ponies and Icelandic horses. Horses without eumelanin (chestnuts) were carriers of the [g.697T; g.1457T] haplotype, but they showed no phenotypic effect. The white or flaxen mane often detected in chestnuts is presumably based on another SILV mutation or on polymorphisms in other genes.
The RYR1 g.1843C>T mutation is associated with the effect of the IGF2 intron3‐g.3072G>A mutation on muscle hypertrophy
Authors: Stinckens A. , Van den Maagdenberg K. , Luyten T. , Georges M. , De Smet S. , Buys N.
Published: January 2007

Muscle growth is a complex phenomenon regulated by many factors, whereby net growth results from the combined action of synthesis and turnover. In pigs, two quantitative trait nucleotides (QTN) are known to have an important influence on muscle growth and fat deposition: one QTN is located in the ryanodine receptor 1 (RYR1) gene (RYR1 g.1843C>T) and the other, a paternally expressed QTN, is in the insulin‐like growth factor 2 (IGF2) gene (IGF2 intron3‐g.3072G>A). The mutation in IGF2 abrogates in vitro interaction with a repressor, which leads to a threefold increase of IGF2 expression in post‐natal muscle. The family of the calpains, a family of Ca2+‐sensitive muscle endopeptidases, and their specific inhibitor calpastatin play an important role in post‐natal protein degradation, also influencing muscle and carcass traits. This study investigated the possible interactions between the genotypes of the RYR1 and IGF2 QTN on IGF2 expression. Samples were taken from several muscles and from pigs at several ages, and messenger RNA expression levels were measured using a real‐time quantification assay. IGF2 expression in m. longissimus dorsi of animals with mutations in both IGF2 and RYR1 was significantly lower than in animals that inherited the IGF2 mutation but were homozygous wildtype for RYR1.
Mitochondrial DNA sequence diversity and origin of Chinese domestic yak
Authors: Lai S.‐J. , Chen S.‐Y. , Liu Y.‐P. , Yao Y.‐G.
Published: January 2007

In order to clarify the origin and genetic diversity of yak in China, we analysed mitochondrial DNA (mtDNA) control region sequences (∼ 891 bp) in 52 individuals from four domestic yak (Poephagus grunniens) breeds, as well as from a hybrid between yak and cattle (Pianniu). Twenty‐five samples were further selected for partial (420 bp) cytochrome b sequencing based on control region sequence information. Two yak samples shared sequences with Chinese cattle (Bos taurus); the remaining yak mtDNAs converged into two major clades in the phylogenetic analysis. Genetic diversity varied substantially among the breeds, with the hybrid Pianniu yak demonstrating the highest diversity. Our results suggest that the Chinese yak was domesticated from two distinct matrilineal sources or from a heterogeneous pool containing both divergent lineages, with occasional gene introgression from cattle.
Genetic diversity and subdivision of 57 European and Middle‐Eastern sheep breeds
Authors: Peter C. , Bruford M. , Perez T. , Dalamitra S. , Hewitt G. , Erhardt G. ,   the ECONOGENE Consortium
Published: January 2007

The population structure and genetic diversity of 57 European and Middle Eastern marginal and cosmopolitan sheep breeds from 15 countries were analysed by typing 31 microsatellite markers. Mean unbiased expected heterozygosities ranged from 0.63 in British Exmoor Horn to 0.77 in Albanian Ruda. South‐eastern European and Middle‐Eastern sheep breeds were significantly more variable than northwestern and western European breeds. An overall heterozygote deficiency (f) across all loci was observed (P < 0.001), while genetic differentiation (θ) was 5.7%. Principal component analysis and Bayesian model‐based clustering indicate a south‐east to north‐west cline, but also revealed distinct groups of Middle‐Eastern fat‐tailed sheep, south‐eastern European sheep and north‐western/western European sheep. Within the last group, two less‐distinct clusters comprised the Merino‐type and Alpine breeds respectively. The incomplete demarcations of most clusters probably reflects cross‐breeding and/or upgrading.