bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficient field emission from Li-salt functionalized multiwall carbon nanotubes on flexible substrates
Authors: Lyth S. M. , Hatton R. A. , Silva S. R. P.
Published: January 2007

The authors report extremely low electron field emission thresholds of 0.25V∕μm from lithium salt functionalized multiwall carbon nanotubes adhered to carbon fiber fabric. Crucially, these nanostructured field emitters are flexible, air stable, and produced via a low cost dip-processing method using an aqueous nanotube ink, whereupon the nanotubes spontaneously assemble onto a surface oxidized carbon fiber matrix to form dense mats. The very low emission threshold is rationalized in terms of the morphology of the nanotube mats and the relatively low work function of lithium salt derivated carbon nanotubes.
Effect of tensile strain on morphology and dielectric property in nanotube/polymer nanocomposites
Authors: Dang Zhi-Min , Yao Sheng-Hong , Xu Hai-Ping
Published: January 2007

As an electrically conducting filler, multiwall carbon nanotube (MWNT) with a great slenderness ratio was introduced into poly(vinylidene fluoride) (PVDF) to form the MWNT/PVDF nanocomposites. Dielectric properties of these composites before and after stretching were studied at wide frequency ranges from 102to107Hz. The results showed that the dielectric constant and conductivity after stretching were always lower than those before stretching. In the composites with high concentration of MWNT, the decreases in dielectric constant and conductivity were very significant. Rearrangement of MWNT in the composites along with the tensile-strain direction could be charge with the results of dielectric properties.
Electrical spin injection and detection in an InAs quantum well
Authors: Koo Hyun Cheol , Yi Hyunjung , Ko Jae-Beom , Chang Joonyeon , Han Suk-Hee , Jung Donghwa , Huh Seon-Gu , Eom Jonghwa
Published: January 2007

The authors demonstrate fully electrical detection of spin injection in InAs quantum wells. A spin-polarized current is injected from a Ni81Fe19 thin film to a two-dimensional electron gas (2DEG) made of InAs based epitaxial multilayers. Injected spins accumulate and diffuse out in the 2DEG, and the spins are electrically detected by a neighboring Ni81Fe19 electrode. The observed spin diffusion length is 1.8μm at 20K. The injected spin polarization across the Ni81Fe19∕InAs interface is 1.9% at 20K and remains at 1.4% even at room temperature. Their experimental results will contribute significantly to the realization of a practical spin field effect transistor.
Signal amplification in a nanomechanical Duffing resonator via stochastic resonance
Authors: Almog Ronen , Zaitsev Stav , Shtempluck Oleg , Buks Eyal
Published: January 2007

The authors experimentally study stochastic resonance in a nonlinear bistable nanomechanical doubly clamped beam resonator, which is capacitively excited by an adjacent gate electrode. The resonator is tuned to its bistability region by an intense pump near a point of equal transition rates between its two metastable states. The pump is amplitude modulated, inducing modulation of the activation barrier between the states. When noise is added to the excitation, resonator’s displacement exhibits noise dependent amplification of the modulation signal. They measure resonator’s response in the time and frequency domains, the spectral amplification, and the statistical distribution of the jump time.
A Study of compressively strained Si0.5Ge0.5 metal-oxide-semiconductor capacitors with chemical vapor deposition HfAlO as gate dielectric
Authors: Huang Jidong , Fu Jia , Zhu Chunxiang , Tay Andrew A. O. , Cheng Zhi-Yuan , Leitz Chris W. , Lochtefeld Anthony
Published: January 2007

The interfacial and electrical properties of metal organic chemical vapor deposited HfAlO on compressively strained Si0.5Ge0.5 (ε-Si0.5Ge0.5) substrate without or with surface nitridation treatment were investigated. X-ray photoelectron spectroscopic analysis suggests that an interfacial layer containing GeOx, Hf silicate, and Al silicate exists on substrates with direct deposition of HfAlO, whereas an interfacial layer containing SiNxOy exists on substrates with surface nitridation prior to HfAlO deposition. The TaN∕HfAlO∕ε-Si0.5Ge0.5 capacitor with surface nitridation shows a larger permittivity of the entire gate dielectric with a thinner interfacial layer (in terms of equivalent oxide thickness), a smaller interface trap charge density, and less severe flatband shift as well as two orders of magnitude lower gate leakage in comparison with those capacitors without nitridation.
Experimental characterization of material nonlinearity using Lamb waves
Authors: Bermes Christian , Kim Jin-Yeon , Qu Jianmin , Jacobs Laurence J.
Published: January 2007

The objective of this research is to develop an accurate and reliable procedure to measure the second order harmonic of a Lamb wave propagating in a metallic plate. There are two associated complications in measuring these nonlinear Lamb waves, namely, their inherent dispersive and multimode natures. To overcome these, this research combines a time-frequency representation with a hybrid wedge generation and laser interferometric detection system. The effectiveness of the proposed procedure is demonstrated by characterizing the inherent material nonlinearity of two different aluminum plates whose absolute nonlinearity parameters are known from longitudinal wave measurements.
Magnetic characterization and switching of Co nanorings in current-perpendicular-to-plane configuration
Authors: Yang T. , Hara M. , Hirohata A. , Kimura T. , Otani Y.
Published: January 2007

The authors fabricated Co nanorings incorporated in the vertical pseudo-spin-valve nanopillar structures with deep submicron lateral sizes. It is shown that the current-perpendicular-to-plane giant magnetoresistance can be used to characterize a very small magnetic nanoring effectively. Both the onion state and the flux-closure vortex state are observed. The Co nanorings can be switched between the onion states as well as between onion and vortex states not only by the external field but also by the perpendicularly injected dc current.
Spatial coherence measurements in arrays of coupled vertical cavity surface emitting lasers
Authors: Lundeberg L. D. A. , Lousberg G. P. , Boiko D. L. , Kapon E.
Published: January 2007

The spatial coherence and the optical phase distribution across a two-dimensional (2D) photonic crystal implemented with coupled arrays of vertical cavity surface emitting lasers (VCSELs) are experimentally characterized. This is achieved by performing Young’s interference experiments between pairs of array elements using a spatial light modulator arrangement. In contrast to far-field measurements that provide information only on the global spatial coherence, this approach can yield full mapping of the complex degree of spatial coherence. Examples of such analysis are presented for nominally uniform one-dimensional and 2D arrays of coupled VCSELs and possible mechanisms of the observed coherence degradation are discussed.
Sexual maturity, factors affecting the breeding season and breeding in consecutive seasons in populations of overabundant Victorian koalas (Phascolarctos cinereus)
Authors: McLean Natasha , Handasyde Kathrine A.
Published: January 2007

It is important to have knowledge of basic population parameters to understand how these vary geographically and temporally and how they contribute to population dynamics. This paper investigates three of these parameters in Victorian koala populations: sexual maturity, aspects of the breeding season, and the continuity of individuals’ breeding. The investigation was carried out in koalas of known-age in two free-living (Redbill Creek on French Island and Brisbane Ranges) and one semi-captive (the Koala Conservation Centre on Phillip Island) population as well as koalas of unknown age in four Victorian populations of overabundant koalas: Mt Eccles and Framlingham in south-west Victoria, French Island in Western Port and Snake Island in south Gippsland. At sexual maturity, female koalas had a mean age (±95% confidence interval) of 24.4 months (23.5–25.3 months), a mean head length of 125 mm (124–127 mm) and a mean body mass of 6.6 kg (6.3–6.8 kg). Only 7.4% of independent females (of unknown age) were carrying young when they weighed less than 6 kg. The breeding season was more restricted in the south-west populations. At Framlingham and Mt Eccles 85% and 91% of births, respectively, occurred between December and March. At Snake and French Islands only 46% and 53% of births, respectively, were recorded in the same period. In the Chlamydia-free population (Red Bill Creek) none of the koalas that were monitored stopped breeding and then resumed breeding in a subsequent season whereas many females from Chlamydia-infected populations (Brisbane Ranges and the Koala Conservation Centre) did so. This variation in reproductive patterns is likely to make an important contribution to the variation in the demography observed in different koala populations.
Genetic affinities among subspecies of a widespread Australian lycaenid butterfly, Ogyris amaryllis (Hewitson)
Authors: Schmidt D. J. , Hughes J. M.
Published: January 2007

Genetic relationships among nominal subspecies of the lycaenid butterfly Ogyris amaryllis were investigated in eastern Australia. High levels of variation and population differentiation observed for allozyme markers were not consistent with subspecies boundaries. Partitioning of allozyme variation was explained better by arranging populations according to their larval host plant. Mitochondrial sequence data recovered a polyphyletic inland subspecies, with several peripheral subspecies showing reduced variation within this topology. Non-parametric topology tests rejected monophyly of the nominal subspecies and suggested that allopatric divergence is unlikely to account for the evolution of this complex. Genetic data, combined with information on distribution and ecology, are more consistent with a pattern of peripheral isolation associated with host-plant specialisation of coastal populations.
Modern origin of numerous alternatively spliced human introns from tandem arrays
Authors: Zhuo Degen , Madden Richard , Elela Sherif Abou , Chabot Benoit
Published: January 2007

Despite the widespread occurrence of spliceosomal introns in the genomes of higher eukaryotes, their origin remains controversial. One model proposes that the duplication of small genomic portions could have provided the boundaries for new introns. If this mechanism has occurred recently, the 5′ and 3′ boundaries of each resulting intron should display distinctive sequence similarity. Here, we report that the human genome contains an excess of introns with perfect matching sequences at boundaries. One-third of these introns interrupt the protein-coding sequences of known genes. Introns with the best-matching boundaries are invariably found in tandem arrays of direct repeats. Sequence analysis of the arrays indicates that many intron-breeding repeats have disseminated in several genes at different times during human evolution. A comparison with orthologous regions in mouse and chimpanzee suggests a young age for the human introns with the most-similar boundaries. Finally, we show that these human introns are alternatively spliced with exceptionally high frequency. Our study indicates that genomic duplication has been an important mode of intron gain in mammals. The alternative splicing of transcripts containing these intron-breeding repeats may provide the plasticity required for the rapid evolution of new human proteins.
Conservation of B class gene expression in the second whorl of a basal grass and outgroups links the origin of lodicules and petals
Authors: Whipple Clinton J. , Zanis Michael J. , Kellogg Elizabeth A. , Schmidt Robert J.
Published: January 2007

Studies of flower development in core eudicot species have established a central role for B class MADS-box genes in specifying petal and stamen identities. Similarly in maize and rice, B class genes are essential for lodicule and stamen specification, suggesting homology of petals and lodicules and conservation of B class gene activity across angiosperms. However, lodicules are grass-specific organs with a morphology distinct from petals, thus their true homology to eudicot and nongrass monocot floral organs has been a topic of debate. To understand the relationship of lodicules to the sterile floral organs of nongrass monocots we have isolated and observed the expression of B class genes from a basal grass
Streptochaeta
that diverged before the evolution of lodicules, as well as the outgroups
Joinvillea
and
Elegia
, which have a typical monocot floral plan. Our results support a conserved role for B function genes across the angiosperms and provide additional evidence linking the evolution of lodicules and second whorl tepal/petals of monocots. The expression data and morphological analysis suggest that the function of B class genes should be broadly interpreted as required for differentiation of a distinct second floral whorl as opposed to specifying petal identity
per se
.
A structural rationale for stalling of a replicative DNA polymerase at the most common oxidative thymine lesion, thymine glycol
Authors: Aller Pierre , Rould Mark A. , Hogg Matthew , Wallace Susan S. , Doublié Sylvie
Published: January 2007

Thymine glycol (Tg) is a common product of oxidation and ionizing radiation, including that used for cancer treatment. Although Tg is a poor mutagenic lesion, it has been shown to present a strong block to both repair and replicative DNA polymerases. The 2.65-Å crystal structure of a binary complex of the replicative RB69 DNA polymerase with DNA shows that the templating Tg is intrahelical and forms a regular Watson–Crick base pair with the incorporated A. The C5 methyl group protrudes axially from the ring of the damaged pyrimidine and hinders stacking of the adjacent 5′ template guanine. The position of the displaced 5′ template guanine is such that the next incoming nucleotide cannot be incorporated into the growing primer strand, and it explains why primer extension past the lesion is prohibited even though DNA polymerases can readily incorporate an A across from the Tg lesion.
Role for rearranged variable gene segments in directing secondary T cell receptor α recombination
Authors: Hawwari Abbas , Krangel Michael S.
Published: January 2007

During the recombination of variable (V) and joining (J) gene segments at the T cell receptor α locus, a VαJα joint resulting from primary rearrangement can be replaced by subsequent rounds of secondary rearrangement that use progressively more 5′ Vα segments and progressively more 3′ Jα segments. To understand the mechanisms that target secondary T cell receptor α recombination, we studied the behavior of a T cell receptor α allele (HYα) engineered to mimic a natural primary rearrangement of TRAV17 to Jα57. The introduced VαJα segment was shown to provide chromatin accessibility to Jα segments situated within several kilobases downstream and to suppress germ-line Jα promoter activity and accessibility at greater distances. As a consequence, the VαJα segment directed secondary recombination events to a subset of Jα segments immediately downstream from the primary rearrangement. The data provide the mechanistic basis for a model of primary and secondary T cell receptor α recombination in which recombination events progress in multiple small steps down the Jα array.
Identification of a subpopulation of cells with cancer stem cell properties in head and neck squamous cell carcinoma
Authors: Prince M. E. , Sivanandan R. , Kaczorowski A. , Wolf G. T. , Kaplan M. J. , Dalerba P. , Weissman I. L. , Clarke M. F. , Ailles L. E.
Published: January 2007

Like many epithelial tumors, head and neck squamous cell carcinoma (HNSCC) contains a heterogeneous population of cancer cells. We developed an immunodeficient mouse model to test the tumorigenic potential of different populations of cancer cells derived from primary, unmanipulated human HNSCC samples. We show that a minority population of CD44
+
cancer cells, which typically comprise <10% of the cells in a HNSCC tumor, but not the CD44
−
cancer cells, gave rise to new tumors
in vivo
. Immunohistochemistry revealed that the CD44
+
cancer cells have a primitive cellular morphology and costain with the basal cell marker Cytokeratin 5/14, whereas the CD44
−
cancer cells resemble differentiated squamous epithelium and express the differentiation marker Involucrin. The tumors that arose from purified CD44
+
cells reproduced the original tumor heterogeneity and could be serially passaged, thus demonstrating the two defining properties of stem cells: ability to self-renew and to differentiate. Furthermore, the tumorigenic CD44
+
cells differentially express the
BMI1
gene, at both the RNA and protein levels. By immunohistochemical analysis, the CD44
+
cells in the tumor express high levels of nuclear BMI1, and are arrayed in characteristic tumor microdomains. BMI1 has been demonstrated to play a role in self-renewal in other stem cell types and to be involved in tumorigenesis. Taken together, these data demonstrate that cells within the CD44
+
population of human HNSCC possess the unique properties of cancer stem cells in functional assays for cancer stem cell self-renewal and differentiation and form unique histological microdomains that may aid in cancer diagnosis.
Colostrum production in swine: from the mammary glands to the piglets.
Authors: Farmer C. , Devillers N. , Rooke J. N. , Dividich J. le
Published: January 2007

An early and high intake of colostrum is a major determinant of survival during the early suckling period, when most losses occur. Indeed, piglets are born devoid of body fat and are dependent on colostrum as their sole energy source. Colostrum also has other essential roles for the developing piglet; most importantly, it provides passive immunity and nutrients to the piglet and permits thermoregulation. It also stimulates gastrointestinal development, muscle protein synthesis and the development of active immunity. Neonatal swine can efficiently use colostrum since they have a remarkable capacity to deposit large amounts of fat and can also absorb intact immunoglobulins for 24 h postnatally. The production of colostrum, however, is very variable between sows and the factors affecting this variability are not well known. Such studies are most difficult to carry out since it is not easy to estimate colostrum yield. Indeed, the various methods that can be used tomeasure colostrum yield all have several drawbacks. The endocrine status of the sow undoubtedly affects the process of colostrogenesis and the underlying mammary changes associated with it. The composition of sow colostrum is well known, yet it is only recently that the presence of numerous bioactive compounds which can either protect piglets from infection or modulate their metabolism was detected in colostral secretions. There are indications that the composition of colostrum can be altered by some management components but further studies are necessary in that area.
Small ruminant mycoplasmoses with particular reference to the Middle East.
Authors: Al-Momani W. , Nicholas R. A. J.
Published: January 2007

Mycoplasmas are responsible for many human and animal diseases and have a tremendous economic and health impact worldwide. They have a pronounced affinity for mucosal surfaces and consequently cause infections of the urogenital and respiratory tracts, but also of the mammary gland and serous membranes, particularly in animals. Mycoplasma infections of small ruminants are known to exist worldwide and cause significant economic impacts because of substantial reductions in milk yield, meat, skins and hair in affected animals; however, little is known of their occurrence in the Middle East. Many mycoplasmas can infect lungs of small ruminants and induce respiratory disease and these
Mycoplasma capricolum
subsp.
capripneumoniae
,
M. mycoides
subsp.
capri
[formerly
M. mycoides
subsp.
mycoides
LC (International Committee on Systematics of Prokaryotes Subcommittee on the Taxonomy of Mollicutes have proposed the merging of these two subspecies into the single subspecies:
M. mycoides
subsp.
capri
; a decision is pending.)] and
Mycoplasma capricolum
subsp.
capricolum
(Mcc).
M. agalactiae
and
M. putrefaciens
can be a major cause of mastitis, arthritis and ocular disease. This review highlights the importance of pathogenic mycoplasmas in small ruminants, including
M. putrefasciens
which has never been described previously in the Middle East. The isolation of mycoplasmas is considered as one of the more difficult tasks for the diagnostic laboratories due to the inability of mycoplasmas to grow easily in laboratory media. The diagnosis of mycoplasma diseases is complex because clinical signs are not characteristic and antibody response can be transient or delayed in the early phase and non-existent in the final stages. Mycoplasma infections are notoriously difficult to prevent and control, rarely responding well to chemotherapy. Many countries control mycoplasma infections by slaughtering the diseased animals, but this way of control is impractical in the Middle East and especially in Jordan where there are limited funds for compensation. Vaccines may be a more efficient way of preventing the spread of disease but are not widely available and those inactivated mycoplasma vaccines that are available may provide only transient protection.
Dietary threonine for broilers: dietary interactions and feed additive supplement use.
Authors: Kidd M. T. , Hackenhaar L.
Published: January 2007

The bird needs amino acids for numerous metabolic functions other than protein synthesis. As nutritionists, we assume that the estimated need of the limiting amino acid, determined by dose-response measurements, reflects the quantitative need of the bird. The global competitiveness of broiler meat production and the variable, and sometimes narrow, profit margins have strengthened the need to feed birds well-balanced diets that meet rather than exceed amino acid needs. The commercial production of L-threonine at prices attractive to least-cost broiler diet formulation has given nutritionists flexibility to decrease crude protein and closer meet the bird's amino acid needs. Care must be taken, however, to ensure that dietary amino acid needs are met, as modern commercial broilers accrete more meat (protein) at earlier ages than previous strains, so any shortage will negatively affect performance. Today, more nutritionists are utilizing the ideal ratio method of formulation. This method assumes ratios of essential amino acids to lysine. Since threonine is generally third limiting after methionine and lysine, the next most limiting amino acid will determine the value of threonine to the nutritionist. Therefore, commercial acceptance of L-threonine emphasizes the importance of accurately defining the minimum amino acid levels of the next limiting amino acids after threonine. Since the relative contribution of amino acids varies by ingredient, it is mportant that we have accurate analyses of all the essential amino acids in the range of ingredients used in formulation. This review discusses key factors that impact threonine needs and our current knowledge of amino acids limiting after threonine.
Review of group size effects on the performance of growing pigs.
Authors: Payne H. G. , Brumm M. C. , DAntuono M. , Pluske J. R. Pluske J. R. , Williams I. H. , Moore K. L. , Mullan B. P.
Published: January 2007

Group size (number of pigs per pen) is an important factor in the design and management of facilities for growing pigs as it can influence capital requirement and the welfare and performance of pigs. Groups of 30 in commercial practice were previously considered as large, whereas today groups of 100-1000 pigs are used on some farms. This review examines early work, previous reviews of group size and recent work on the effect of group size on pig performance. The paper also incorporates an analysis of 19 recently published studies. The analysis showed that increasing group size from 5 to 100 pigs per pen appeared to have a small, negative effect on performance of weaner and finisher pigs provided that floor-space, and the number of feeders and drinkers was adequate. Group size appeared to have a greater impact on grower pigs, but this may be a reflection of the shorter duration of these particular studies. The review also describes a number of factors that may interact or be influenced by group size. These include carcass characteristics, behaviour, crowding, pen size and shape, and provision of resources such as feeders and drinkers. It can be concluded that pig behaviour alters with increasing group size and that much remains to be understood about pig behaviour in groups of 30-40 pigs and upwards. In practice, while housing pigs in large groups decreases construction, maintenance and cleaning costs, it may increase labour associated with inspection, treatment and marketing of pigs.
The assessment of pain in cattle: a review.
Authors: Stafford K. J. , Mellor D. J.
Published: January 2007

The assessment of pain in cattle is hindered by the difficulty of communication between species and the possibility that prey species, such as cattle, limit behaviour indicative of pain due to the danger of predation. To identify behavioural and physiological responses caused by the pain of any surgical procedure, injury or disease, it is necessary to compare the responses of animals that have received or not received effective local anaesthesia or analgesia. Few such studies have been carried out. The responses of animals to any injury may be due to irritation, dysfunction or be part of the convalescence process and may not be caused by pain
per se
. Specific behaviours may indicate pain following specific injuries. The pain caused by different injuries may evoke specific behaviours so many sets of observations are required to define the behaviours evoked by pain. Head and tail shaking and the lack of grooming and rumination are useful indicators of pain after dehorning but there is a need to quantify whether these behaviours are useful indicators of pain following other injuries by further behavioural observational studies. Generally, behaviour is most useful in a clinical situation. However, physiological responses to different procedures, such as the plasma cortisol response, can be used to compare the relative painfulness of different experiences under experimental conditions and the results of this type of research can then be used clinically. Changes in productivity and immunocompetence during and following a painful experience are probably not useful tools to measure pain. Behaviour and physiological responses are useful ways to assess acute pain but there are problems with the assessment of chronic pain. The response of cattle to specific stimuli (mechanical, pressure and thermal) may be useful to measure chronic pain. Much work is required to confirm that specific behaviours or the absence of them are useful general indicators of pain in cattle and to identify those behaviours which may be useful indicators of pain after specific injuries.
Geographical information systems and remote sensing in veterinary disease mapping.
Authors: Rinaldi L. , Biggeri A. , Cringoli G.
Published: January 2007

Disease mapping and risk assessment are important tasks in the area of medical and veterinary epidemiology. The development of methods for mapping diseases has progressed considerably in recent years. Geographical information systems (GIS) and remote sensing (RS) represent new tools for the study of epidemiology, and their application to veterinary medicine, and in particular to parasitology, has become more and more advanced to study the spatial and temporal patterns of diseases. The present review highlights the usefulness of GIS and RS for: disease mapping, ecological analysis, and surveillance and monitoring of animal diseases.
Biotechnology of
Curcuma
.
Authors: Parthasarathy V.A. , Sasikumar B.
Published: January 2007

Curcuma
is gaining importance globally as a potential source of drugs to combat a variety of ailments. Biotechnological intervention in the genus is almost two decades old. Though earlier studies of
Curcuma
biotechnology were focused mainly on standardization of tissue culture protocols, recent attention has been towards molecular biology aspects of the genus. This review gives up-to-date information on the various aspects of
Curcuma
biotechnology such as tissue culture protocol standardization, in vitro conservation,
in vitro
screening,
in vitro
microrhizome induction and
in vitro
pollination besides molecular biology studies.
Applications of RNA interference in transgenic plants.
Authors: Müllerr A.E.
Published: January 2007

RNA interference (RNAi) is a powerful tool to down-regulate single genes or sets of genes in a sequence-specific manner. Since its discovery in the 1990s, an impressive amount of research has revealed many of the key steps and players that produce the small RNA species at the centre of the mechanism of RNAi (i.e., small interfering RNAs and microRNAs), or mediate the downstream events that result in post-transcriptional and/or transcriptional inhibition of target gene activity. Experiments are also underway to identify the precise parameters that determine the effectiveness and specificity of the initial trigger of RNAi, and to elucidate the immediate and longer-term consequences of RNAi at the target locus. With increasing knowledge of all phases of RNAi, from induction to maintenance and propagation, the potential of RNAi as a biotechnological tool and the spectrum of its applications will continue to widen. In this review, some of the most promising technical advances of RNAi in transgenic plants will be laid out, as well as current and possible future applications.
The importance of the genotype×environment interaction for selection and breeding programmes in tropical conditions.
Authors: Menèndez Buxadera A. , Mandonnet N.
Published: January 2007

The literature on genotype × environment interaction (I
GE
) was reviewed and discussed in order to obtain an overview of its effects for breeding programmes in tropical conditions. The results from cattle were the example used, owing to the great number of references available. The evidence shows that the performance of a specialized dairy breed introduced in the tropics is very far from the expected results and the best sires in the exporter countries (developed countries) were not the best in the tropical countries (importer). This same trend was found when the results from
Bos taurus
×
Bos indicus
crossbreeding programmes were examined. The publications for beef cattle show ahigh level of genetic correlations between the breeding value of the sires estimated in different countries. However, when the level of connection between animals was taken into account, the effect of I
GE
was evident. The importance of I
GE
was also found between countries with a high level of concentrate versus pasture feeding base: the same results were published for tropical conditions. A very large dataset of milk production statistics for the tropics (more than 200 000 records) was analysed in order to present some results on I
GE
based on a more robust statistical procedure. In this study, the milk production level of the herd was used as an environmental variable and the genetic parameters were estimated by a classical simple sire model, a character state model (CSM) and a reaction norm model (RNM). The results from RNM were considered to be the best, and allowed the estimation of the evolution of genetic variance in the entire trajectory of environment (22005000 kg of milk production). A clear effect of I
GE
was evident and the best sires in a low environmental level were not the best in a high environmental level. A large genetic variability in plasticity was detected. Accordingly, the use of RNM is highly recommended in tropical breeding programmes because it allows the identification of the more adapted sires to heterogeneous environment. More research is needed for a better understanding of I
GE
in the tropics, particularly more collaboration between tropical countries is necessary ... it is a dream to establish a tropical Interbull that enables us to reach the same results as those obtained in developed countries!
Recent developments in vaccination against the major nematode parasites of livestock.
Authors: Knox D. P.
Published: January 2007

This review summarizes the major developments towards developing vaccines against the major nematode infections of livestock, principally cattle and sheep. The drivers for vaccine development and factors likely to influence the required efficacy and performance are discussed. Subunit vaccine progress is summarized with antigens discussed being proteins that are required for feeding, are excreted/secreted from the parasite, or are specifically targeted by the immune response of animals exposed to infection which then develop immunity. Challenges to vaccine development are outlined including recombinant protein production, target identification and validation and methods for vaccine delivery to the immune system. The review concludes by addressing some of the market factors which will influence vaccine uptake.
Traceability in the agri-food sector: issues, insights and implications.
Authors: Hobbs J. E.
Published: January 2007

Traceability of food and food ingredients from farm to fork has become an important issue for agri-food firms and policymakers, and is the subject of a growing body of research. This paper provides a review of recent literature dealing with the economic and supply chain management implications of traceability. The definitions, scope and functions of traceability are reviewed, reflecting the multifaceted nature of traceability, which ranges from simple identification, to full chain traceability, to traceback coupled with the proactive provision of information on product origin, movement, production and processing methods. In this vein, a variety of roles for traceability systems is apparent: from minimizing the impact of food safety and herd health problems, to more efficient management of supply chain logistics, to traceability systems that also facilitate quality assurances with respect to credence attributes. Traceability has more value for consumers when bundled with credible quality assurances. The implications for producers are best assessed through understanding the relative market-based incentives (management of supply chains, reduced recalls, product differentiation opportunities) versus the disincentives (implementation and maintenance costs) to adopt traceability systems. Future research could enhance our understanding of consumer perceptions with respect to traceability and quality assurances; it could provide a quantitative assessment of the relative costs and benefits (private and public) of adopting traceability systems. Future research could also explore the pivotal role of food retailers and food service companies with respect to traceability requirements from their suppliers, the role of third party verification, and the implications for supply chain relationships.
Sustainable practices to limit soil erosion: a review and discussion.
Authors: Evans R.
Published: January 2007

How the review was carried out is briefly described. The review looks mainly at the literature published since year 2000, but does not exclude earlier publications. The sustainability of practices to limit erosion must be assessed not only in terms of the soil resource and the wider environment but must also take into account economical and socio-political factors. Soil degradation may be due to a number of causes and it may be that in places erosion is not the main factor. So how erosion is assessed and perceived may be an important factor if degradation is to be successfully tackled. Certainly, in many parts of the world farmers do not, or cannot, combat erosion. A brief history of soil conservation practices is given and then these techniques are examined in more detail in terms of their environmental, economical and socio-political sustainability. Many practices are environmentally sustainable, especially those used by small indigenous farmers, but few are sustainable in financial and socio-political terms. Although conservation tillage techniques are being vigorously promoted they may be more sustainable when carried out on small farms where no herbicide inputs are needed. It is the economical and socio-political factors that lead to erosion which need to be tackled if sustainable practices to limit soil erosion are to be successful.
The alleviation of pain in cattle: a review.
Authors: Stafford K. J. , Chambers J. P. , Mellor D. J.
Published: January 2007

The alleviation of pain in cattle is dependent on the ability to recognise pain and to determine whether systemic analgesia or local anaesthesia is effective. Local and regional anaesthesia have long been used to reduce pain and its attendant behaviours during surgery in conscious cattle, but concern about post-operative pain and its alleviation are more recent developments. A number of classes of analgesics (opioids, non-steroidal anti-inflammatory drugs (NSAIDs), alpha-2 adrenoreceptor agonists) are used in cattle to alleviate pain caused by surgery, injury or disease. These drugs can be useful analgesics, but their use is limited by concern about residues and cost. The NSAID, ketoprofen, has been shown to be an effective analgesic after dehorning and castration when combined with local anaesthesia in calves. Xylazine is also an effective analgesic but there is very limited information on the analgesic effects in cattle of many other drugs. There are a limited number of drugs registered for use in cattle and it is important that local anaesthetics and systemic analgesics are available to alleviate pain in this species at prices which make them economically attractive.
The role of nutrition in cataract formation in farmed fish.
Authors: Bjerkås E. , Breck O. , Waagbo R.
Published: January 2007

A brief overview of the lens anatomy and biochemistry, characteristics of cataract development in fish, as well as diagnostic techniques and evaluation of findings are given, before the role of nutrition on cataract development in fish is discussed. Nutritionally related cataracts are described based on single nutrient groups. However, in most of the studies on nutrition and cataract, interactions between several nutrients cannot be excluded, especially observed in relation to the major changes in feed composition during the last decades and the search for alternative feed ingredients. Environmental factors in aquaculture, as well as differences between fish species and strains within a species may also affect cataract development. Thus, although nutritional factors have been shown to be important in the pathogenesis of cataract, cataract occurring in modern intensive fish farming should be considered a production-related multifactorial disorder.
Cre/
lox
technologies for plant transformation.
Authors: Srivastava V. , Nicholson S. J.
Published: January 2007

Several methods for transferring foreign genes into plant cells have been developed in last 20 years; however, very little progress has been made towards controlling transgene integration into the plant genome. Since stable transgene expression entails precise single-copy integration, controlling the integration process is extremely important for optimizing transformation technologies. One of the most effective strategies for engineering single-copy structure is utilization of site-specific recombination (SSR) systems derived from prokaryotes and lower eukaryotes. Cre/
lox
, FLP/
FRT
, R/
RS
and FC31 are some of the SSR systems shown to be functional in plant cells, with Cre/
lox
displaying the highest efficiency among all. When Cre recombinase is available, sequences bordered by
lox
sites may excise or invert, dependent upon the relative orientation of interacting
lox
sites. This principle has been utilized for developing a number of different technologies, including marker gene deletion and transgene integration. Owing to its remarkable efficiency and undetectable toxicity in plant cells, Cre/
lox
system has emerged as one of the most promising tools for plant biotechnology.
Managing risk in clonal forestry.
Authors: Burdon R. D. , Aimers-Halliday J.
Published: January 2007

Risks associated with clonal forestry are mainly biological. Among such risks, propagation failure, cultivar decline, and imperfect clonal evaluation all call for specific, targeted countermeasures; delayed failure of clones, however, calls mainly for risk spread. Propagation failures often reduce genetic gain and/or narrow the genetic base. Cultivar decline typically stems from maturation, especially in conifers, and can preclude successful clonal forestry. Maturation can be much delayed by hedging, serial propagation, coppicing (if possible), and cold-storage of tissue, but effectively halting maturation probably requires embryogenesis together with cryogenic storage. Totally restoring juvenility in vegetative material is an ideal, but it is still seldom achievable. Other possibleforms of cultivar decline include plagiotropism, and virus infection in hardwoods. Inadequate clonal evaluation can lead to delayed underperformance, especially where genotype-site interaction is important. Clonal failure can result from biotic and climatic events, which may be unpredictable. Climatic damage may affect only occasional clones, but biotic damage is often more comprehensive. Risk spread, however, will not counter agents that cause unacceptable failure rates among deployed clones. Theoretically, as the effective number of unrelated clones exceeds about 20, the additional protection conferred by risk spread becomes marginal, and genetic gain can become significantly eroded. How to deploy a portfolio of clones, in options ranging from intimate mixture to monoclonal mosaics, is debatable. The appropriate choice can depend on various factors, including the nature of likely damage, the epidemiology of the pathogen or insect pest, the silvicultural regime, and the logistics of possible salvage harvesting.
Nuclear repositioning of the VSG promoter during developmental silencing in Trypanosoma brucei
Authors: Landeira David , Navarro Miguel
Published: January 2007

Interphase nuclear repositioning of chromosomes has been implicated in the epigenetic regulation of RNA polymerase (pol) II transcription. However, little is known about the nuclear position–dependent regulation of RNA pol I–transcribed loci. Trypanosoma brucei is an excellent model system to address this question because its two main surface protein genes, procyclin and variant surface glycoprotein (VSG), are transcribed by pol I and undergo distinct transcriptional activation or downregulation events during developmental differentiation. Although the monoallelically expressed VSG locus is exclusively localized to an extranucleolar body in the bloodstream form, in this study, we report that nonmutually exclusive procyclin genes are located at the nucleolar periphery. Interestingly, ribosomal DNA loci and pol I transcription activity are restricted to similar perinucleolar positions. Upon developmental transcriptional downregulation, however, the active VSG promoter selectively undergoes a rapid and dramatic repositioning to the nuclear envelope. Subsequently, the VSG promoter region was subjected to chromatin condensation. We propose a model whereby the VSG expression site pol I promoter is selectively targeted by temporal nuclear repositioning during developmental silencing.
Igκ allelic inclusion is a consequence of receptor editing
Authors: Casellas Rafael , Zhang Qingzhao , Zheng Nai-Ying , Mathias Melissa D. , Smith Kenneth , Wilson Patrick C.
Published: January 2007

The discovery of lymphocytes bearing two light chains in mice carrying self-reactive antibody transgenes has challenged the “one lymphocyte–one antibody” rule. However, the extent and nature of allelically included cells in normal mice is unknown. We show that 10% of mature B cells coexpress both Igκ alleles. These cells are not the result of failure in allelic exclusion per se, but arise through receptor editing. We find that under physiological conditions, editing occurs both by deletion and by inclusion with equal probability. In addition, we demonstrate that B lymphocytes carrying two B-cell receptors are recruited to germinal center reactions, and thus fully participate in humoral immune responses. Our data measure the scope of allelic inclusion and provide a mechanism whereby autoreactive B cells might “escape” central tolerance.
Induced sensitization of tumor stroma leads to eradication of established cancer by T cells
Authors: Zhang Bin , Bowerman Natalie A. , Salama Joseph K. , Schmidt Hank , Spiotto Michael T. , Schietinger Andrea , Yu Ping , Fu Yang-Xin , Weichselbaum Ralph R. , Rowley Donald A. , Kranz David M. , Schreiber Hans
Published: January 2007

Targeting cancer cells, as well as the nonmalignant stromal cells cross-presenting the tumor antigen (Ag), can lead to the complete destruction of well-established solid tumors by adoptively transferred Ag-specific cytotoxic T lymphocytes (CTLs). If, however, cancer cells express only low levels of the Ag, then stromal cells are not destroyed, and the tumor escapes as Ag loss variants. We show that treating well-established tumors expressing low levels of Ag with local irradiation or a chemotherapeutic drug causes sufficient release of Ag to sensitize stromal cells for destruction by CTLs. This was shown directly using high affinity T cell receptor tetramers for visualizing the transient appearance of tumor-specific peptide–MHC complexes on stromal cells. Maximum loading of tumor stroma with cancer Ag occurred 2 d after treatment and coincided with the optimal time for T cell transfer. Under these conditions, tumor rejection was complete. These findings may set the stage for developing rational clinical protocols for combining irradiation or chemotherapy with CTL therapy.
Reductive evolution and niche adaptation inferred from the genome of Mycobacterium ulcerans, the causative agent of Buruli ulcer
Authors: Stinear Timothy P. , Seemann Torsten , Pidot Sacha , Frigui Wafa , Reysset Gilles , Garnier Thierry , Meurice Guillaume , Simon David , Bouchier Christiane , Ma Laurence , Tichit Magali , Porter Jessica L. , Ryan Janine , Johnson Paul D.R. , Davies John K. , Jenkin Grant A. , Small Pamela L.C. , Jones Louis M. , Tekaia Fredj , Laval Françoise , Daffé Mamadou , Parkhill Julian , Cole Stewart T.
Published: January 2007

Mycobacterium ulcerans is found in aquatic ecosystems and causes Buruli ulcer in humans, a neglected but devastating necrotic disease of subcutaneous tissue that is rampant throughout West and Central Africa. Here, we report the complete 5.8-Mb genome sequence of M. ulcerans and show that it comprises two circular replicons, a chromosome of 5632 kb and a virulence plasmid of 174 kb. The plasmid is required for production of the polyketide toxin mycolactone, which provokes necrosis. Comparisons with the recently completed 6.6-Mb genome of Mycobacterium marinum revealed >98% nucleotide sequence identity and genome-wide synteny. However, as well as the plasmid, M. ulcerans has accumulated 213 copies of the insertion sequence IS2404, 91 copies of IS2606, 771 pseudogenes, two bacteriophages, and multiple DNA deletions and rearrangements. These data indicate that M. ulcerans has recently evolved via lateral gene transfer and reductive evolution from the generalist, more rapid-growing environmental species M. marinum to become a niche-adapted specialist. Predictions based on genome inspection for the production of modified mycobacterial virulence factors, such as the highly abundant phthiodiolone lipids, were confirmed by structural analyses. Similarly, 11 protein-coding sequences identified as M. ulcerans-specific by comparative genomics were verified as such by PCR screening a diverse collection of 33 strains of M. ulcerans and M. marinum. This work offers significant insight into the biology and evolution of mycobacterial pathogens and is an important component of international efforts to counter Buruli ulcer.