bluuebunny/crossref_metadata_2025 huggingface dataset:
An improved SVAT model calibration strategy based on the optimisation of surface temperature temporal dynamics
Authors: Coudert B. , Ottlé C.
Published: February 2007

Various studies have demonstrated the potential of thermal infrared brightness temperature (TIR TB) for monitoring surface exchanges of water and energy. This study focuses on the contribution of TIR TB data for Land Surface Model (LSM) calibration. A numerical representation of the Soil‐Vegetation‐Atmosphere (SVA) transfers (SVAT model), named SEtHyS, was used. A calibration methodology of the model based uniquely on the optimisation of TIR TB diurnal cycle features has been developed and applied, in an assimilation context, to the full vegetation period of a wheat crop. The results illustrate the advantages of such a methodology for the monitoring of environmental conditions simulated with the SVAT model, such as the root zone soil moisture. The impact of observation and simulation errors on TIR TB was analysed and quantified in controlled numerical experiments. The results demonstrate the advantages of using relative temperature characteristics, instead of temperature values themselves, to minimise the impact of noise.
Particle number to volume concentration ratios at two measurement sites in Finland
Authors: Kivekäs Niku , Kerminen Veli‐Matti , Engler Christa , Lihavainen Heikki , Komppula Mika , Viisanen Yrjö , Kulmala Markku
Published: February 2007

Past studies have indicated that the aerosol number to volume concentration ratio R, defined as the number concentration of particles larger than a certain cutoff diameter divided by the total particle volume concentration, shows little variability in marine conditions. In this study, aerosol number size distributions from Pallas in northern Finland and from the island of Utö in the Baltic Sea, representing more continental aerosol systems, were analyzed. The data set covered continuous measurements for 20 months at Pallas and 21 months at Utö. The average value and standard deviation of R, calculated from the measured data, were found to be inversely dependent on the cutoff diameter used, dc. The average value of R (in μm−3) could be expressed as R(dc) = 22,000 × dc−1 + 20 (where dc is in nm) in Pallas and R(dc) = 40,000 × dc−1 − 160 in Utö in dc range 50–200 nm. Also, the relative deviation (standard deviation divided by average value) of R(dc) was found to be dependent on the cutoff diameter. A clear seasonal pattern of the values of R was observed at both sites, and this was found to be related to ambient temperature. The value of R was found to depend on the air mass type at Pallas, but at Utö such dependency was not observed. Besides temperature, R was also analyzed against several meteorological parameters, including global solar radiation, air pressure, relative humidity, and rain. The found dependencies between the number of potential cloud condensation nuclei and particle volume concentration provide tools for developing more accurate empirical parameterizations describing cloud formation in large‐scale atmospheric models.
A generalized formulation of the protection ratio applicable to frequency coordination in digital radio relay networks
Authors: Suh Kyoung Whoan
Published: February 2007

This paper proposes an efficient and comprehensive algorithm for computing the protection ratio and illustrates some results applicable to the initial planning of frequency coordination for fixed wireless networks. A net filter discrimination depending upon transmitter spectrum mask and overall receiver filter characteristic is also examined to see the effect of adjacent channel interferences. Numerical simulations for cochannel and adjacent channel protection ratios are performed for the 6.2 GHz frequency band, including transmitter spectrum mask and receiver filter response. According to results for 64‐QAM (quadrature amplitude modulation) and 60 km at bit error ratio 10−6, fade margin and cochannel protection ratio are 41.1 and 74.9 dB, respectively. In addition, it is shown that the net filter discrimination for 30 MHz channel bandwidth provides 26.5 dB at the first adjacent channel, which yields adjacent channel protection ratio of 48.4 dB. The proposed method gives an easy and systematic method to compute the protection ratio and can be applied to frequency coordination in fixed wireless networks up to the millimeter wave band.
The regulatory role of TGF‐β in airway remodeling in asthma
Authors: Makinde Toluwalope , Murphy Richard F , Agrawal Devendra K
Published: February 2007

Both structural and inflammatory cells are capable of secreting transforming growth factor (TGF)‐β and expressing TGF‐β receptors. TGF‐β can induce multiple cellular responses including differentiation, apoptosis, survival and proliferation, and has been implicated in the development of several pathogenic conditions including cancer and asthma. Elevated levels of TGF‐β have been reported in the asthmatic airway. TGF‐β binds to its receptor complex and activates multiple pathways involving proteins such as Sma and Mad homologues, phosphatidylinositol‐3 kinase and the mitogen‐activated protein kinases, leading to the transcription of several genes. Cell type, cellular condition, and microenvironment, all play a role in determining which pathway is activated, which, in turn, is an indication of which gene is to be transcribed. TGF‐β has been shown to induce apoptosis in airway epithelial cells. A possible role for TGF‐β in the regulation of epithelial cell adhesion properties has also been reported. Enhancement of goblet cell proliferation by TGF‐β suggests a role in mucus hyper‐secretion. Elevated levels of TGF‐β correlate with subepithelial fibrosis. TGF‐β induces proliferation of fibroblast cells and their differentiation into myofibroblasts and extracellular matrix (ECM) protein synthesis during the development of subepithelial fibrosis. TGF‐β also induces proliferation and survival of and ECM secretion in airway smooth muscle cells (ASMCs), suggesting a possible cause of increased thickness of airway tissues. TGF‐β also induces the production and release of vascular endothelial cell growth factor and plasminogen activator inhibitor, contributing to the vascular remodeling in the asthmatic airway. Blocking TGF‐β activity inhibits epithelial shedding, mucus hyper‐secretion, angiogenesis, ASMC hypertrophy and hyperplasia in an asthmatic mouse model. Reduction of TGF‐β production and control of TGF‐β effects would be beneficial in the development of therapeutic intervention for airway remodeling in chronic asthma.
Optimising bait-station delivery of fertility control agents to brushtail possum populations
Authors: Tompkins Daniel M. , Ramsey David
Published: February 2007

Introduced Australian brushtail possums (Trichosurus vulpecula) are a major pest in New Zealand. Alternatives to current management by trapping and poisoning are being actively explored. The most effective scenario for the deployment of fertility control vaccines is the use of bait stations to maintain possum populations at low densities following their initial knockdown from high densities using conventional control tools. However, three field trials that estimated population coverage achievable by differing station layouts using dyed baits have produced conflicting results. To assess optimal vaccine-delivery strategies adequately we need meaningful a priori expectations of the level of population coverage achievable by differing bait station layouts and densities. To this end, we collated data on field operations in which bait stations were used to deliver acute toxins for lethal control of possum populations and constructed an individual-based spatially explicit stochastic model to simulate encounter rates between possums and bait stations. The model provided a reasonable fit to the data from both the acute toxin operations and two of the three dyed-bait trials. The third trial likely overestimated typical possum movement distances. Simulating vaccine delivery in the model demonstrated that grid densities of 0.6 bait stations ha–1 are predicted to be optimal, and prefeeding may not be necessary. The model strongly indicates that the effective delivery of fertility control will not be limited by our ability to deliver vaccine baits to possums. However, the exact strategy to employ will depend on three key characteristics of any vaccine – its expense relative to existing tools, its longevity in the field, and its efficacy at reducing female breeding success.
Breeding-site selection by cane toads (Bufo marinus) and native frogs in northern New South Wales, Australia
Authors: Semeniuk M. , Lemckert F. , Shine R.
Published: February 2007

Previous research on cane toads (Bufo marinus) has documented non-random selection of breeding sites by this invasive species. In the wet–dry tropics of the Northern Territory, toads selected spawning sites in open areas with gently sloping banks and shallow water. If consistent, such biases may present opportunities for toad control via waterbody manipulation – but first we need to know whether such criteria for spawning-site selection (1) are consistent across other parts of the toad’s extensive Australian range, and (2) differ from those of native anurans breeding at the same waterbodies. We quantified the attributes of potential and actual spawning-sites in north-eastern New South Wales, in temperate-zone habitat where cane toads have been present for many decades; our study area thus differs in many ways from the previously studied tropical site. We compared habitat and water chemistry variables between 23 cane toad breeding sites and 23 nearby unused sites. To examine habitat use at an even finer scale, we conducted nocturnal surveys of microhabitat use by calling male toads and native anurans. Our results revealed that cane toads in this region were highly selective in their choice of breeding sites, and that the criteria they used in this respect were similar to those used by toads in the Northern Territory. Calling male cane toads also used microhabitats non-randomly within each pond, apparently based on similar criteria to those used when selecting among ponds. Toads differed significantly from native anurans in these respects, suggesting that it may be feasible to manipulate waterbody attributes to impact on invasive toads without disrupting reproduction by native anurans.
Stable masking by H-2Ddcis ligand limits Ly49A relocalization to the site of NK cell/target cell contact
Authors: Back Jonathan , Chalifour Anick , Scarpellino Léonardo , Held Werner
Published: February 2007

Ly49A is an inhibitory receptor, which counteracts natural killer (NK) cell activation on the engagement with H-2Dd(Dd) MHC class I molecules (MHC-I) on target cells. In addition to binding Ddon apposed membranes, Ly49A interacts with Ddligand expressed in the plane of the NK cells' membrane. Indeed, multivalent, soluble MHC-I ligand binds inefficiently to Ly49A unless the NK cells' Ddcomplexes are destroyed. However, it is not known whether masked Ly49A remains constitutively associated with cis Ddalso during target cell interaction. Alternatively, it is possible that Ly49A has to be unmasked to significantly interact with its ligand on target cells. These two scenarios suggest distinct roles of Ly49A/Ddcis interaction for NK cell function. Here, we show that Ly49A contributes to target cell adhesion and efficiently accumulates at synapses with Dd-expressing target cells when NK cells themselves lack Dd. When NK cells express Dd, Ly49A no longer contributes to adhesion, and ligand-driven recruitment to the cellular contact site is strongly reduced. The destruction of Ddcomplexes on NK cells, which unmasks Ly49A, is necessary and sufficient to restore Ly49A adhesive function and recruitment to the synapse. Thus, cis Ddcontinuously sequesters a considerable fraction of Ly49A receptors, preventing efficient Ly49A recruitment to the synapse with Dd+ target cells. The reduced number of Ly49A receptors that can functionally interact with Ddon target cells explains the modest inhibitory capacity of Ly49A in DdNK cells. This property renders Ly49A NK cells more sensitive to react to diseased host cells.
Two forms of single-vesicle astrocyte exocytosis imaged with total internal reflection fluorescence microscopy
Authors: Bowser David N. , Khakh Baljit S.
Published: February 2007

Transmitters such as glutamate and ATP are released from brain astrocytes. Several pathways for their release have been proposed, including exocytosis. In the present study we sought to measure exocytosis from astrocytes with single vesicle imaging methods using synaptopHlourin (SpH) as an optical reporter. We imaged single SpH-laden vesicles with total internal reflection fluorescence (TIRF) microscopy. We observed spontaneous, as well as evoked, single-vesicle exocytosis events. Analysis of the kinetics and spatial spread associated with these events indicated two discernible forms of single vesicle exocytosis. One form, constituting ≈40% of the spontaneous events, was akin to kiss-and-run vesicle fusion and captured a mobile proton buffer from the extracellular medium. The other form seems to represent full vesicle fusion, constitutes ≈60% of the spontaneous events, and is associated with complete mixing of the vesicle and plasma membranes. Activation of calcium-mobilizing receptors on the astrocyte surface selected between the different forms of exocytosis. These data provide evidence for two forms of simultaneously occurring single-vesicle exocytosis events in astrocytes, and also suggest that SpH imaging and TIRF microscopy is useful to study the mechanisms of astrocyte transmitter release.
Structure of the Parkin in-between-ring domain provides insights for E3-ligase dysfunction in autosomal recessive Parkinson's disease
Authors: Beasley Steven A. , Hristova Ventzislava A. , Shaw Gary S.
Published: February 2007

Mutations in Parkin are one of the predominant hereditary factors found in patients suffering from autosomal recessive juvenile Parkinsonism. Parkin is a member of the E3 ubiquitin ligase family that is defined by a tripartite RING1-in-between-ring (IBR)-RING2 motif. In Parkin, the IBR domain has been shown to augment binding of the E2 proteins UbcH7 and UbcH8, and the subsequent ubiquitination of the proteins synphilin-1, Sept5, and SIM2. To facilitate our understanding of Parkin function, the solution structure of the Parkin IBR domain was solved by using NMR spectroscopy. Folding of the IBR domain (residues M327–S378) was found to be zinc dependent, and the structure reveals the domain forms a unique pair scissor-like and GAG knuckle-like zinc-binding sites, different from other zinc-binding motifs such as the RING, LIM, PHD, or B-box motifs. The N terminus of the IBR domain, residues E307–E322, is unstructured. The disease causing mutation T351P causes global unfolding, whereas the mutation R334C causes some structural rearrangement of the domain. In contrast, the protein containing the mutation G328E appears to be properly folded. The structure of the Parkin IBR domain, in combination with mutational data, allows a model to be proposed where the IBR domain facilitates a close arrangement of the adjacent RING1 and RING2 domains to facilitate protein interactions and subsequent ubiquitination.
Unified picture of the oxygen isotope effect in cuprate superconductors
Authors: Chen Xiao-Jia , Struzhkin Viktor V. , Wu Zhigang , Lin Hai-Qing , Hemley Russell J. , Mao Ho-kwang
Published: February 2007

High-temperature superconductivity in cuprates was discovered almost exactly 20 years ago, but a satisfactory theoretical explanation for this phenomenon is still lacking. The isotope effect has played an important role in establishing electron–phonon interaction as the dominant interaction in conventional superconductors. Here we present a unified picture of the oxygen isotope effect in cuprate superconductors based on a phonon-mediated
d
-wave pairing model within the Bardeen–Cooper–Schrieffer theory. We show that this model accounts for the magnitude of the isotope exponent as functions of the doping level as well as the variation between different cuprate superconductors. The isotope effect on the superconducting transition is also found to resemble the effect of pressure on the transition. These results indicate that the role of phonons should not be overlooked for explaining the superconductivity in cuprates.
Inhibition of regulated proteolysis by RseB
Authors: Cezairliyan Brent O. , Sauer Robert T.
Published: February 2007

The
Escherichia coli
envelope-stress response is a sensor system that increases transcription of stress genes in the cytoplasm when misfolded porins are detected in the periplasm. This response is initiated by DegS cleavage of the periplasmic domain of RseA, a transmembrane protein. Additional proteolysis of transmembrane and cytoplasmic portions of RseA then frees the σ
E
transcription factor, which directs the transcriptional response. We show that RseB protein, a known negative regulator, inhibits proteolysis by DegS
in vitro
by binding tightly to the periplasmic domain of RseA. Inhibition of DegS cleavage requires RseB binding to a conserved region near the C terminus of the poorly structured RseA domain, but the RseA sequences that mediate DegS recognition and RseB binding do not overlap directly. Although DegS cleavage of RseA is normally activated by binding of the C termini of porins to the PDZ domain of DegS, RseB inhibition is independent of this activation mechanism.
Structures of the extracellular regions of the group II/III metabotropic glutamate receptors
Authors: Muto Takanori , Tsuchiya Daisuke , Morikawa Kosuke , Jingami Hisato
Published: February 2007

Metabotropic glutamate receptors play major roles in the activation of excitatory synapses in the central nerve system. We determined the crystal structure of the entire extracellular region of the group II receptor and that of the ligand-binding region of the group III receptor. A comparison among groups I, II, and III provides the structural basis that could account for the discrimination of group-specific agonists. Furthermore, the structure of group II includes the cysteine-rich domain, which is tightly linked to the ligand-binding domain by a disulfide bridge, suggesting a potential role in transmitting a ligand-induced conformational change into the downstream transmembrane region. The structure also reveals the lateral interaction between the two cysteine-rich domains, which could stimulate clustering of the dimeric receptors on the cell surface. We propose a general activation mechanism of the dimeric receptor coupled with both ligand-binding and interprotomer rearrangements.
CCR7 ligands stimulate the intranodal motility of T lymphocytes in vivo
Authors: Worbs Tim , Mempel Thorsten R. , Bölter Jasmin , von Andrian Ulrich H. , Förster Reinhold
Published: February 2007

In contrast to lymphocyte homing, little is known about molecular cues controlling the motility of lymphocytes within lymphoid organs. Applying intravital two-photon microscopy, we demonstrate that chemokine receptor CCR7 signaling enhances the intranodal motility of CD4+ T cells. Compared to wild-type (WT) cells, the average velocity and mean motility coefficient of adoptively transferred CCR7-deficient CD4+ T lymphocytes in T cell areas of WT recipients were reduced by 33 and 55%, respectively. Both parameters were comparably reduced for WT T lymphocytes migrating in T cell areas of plt/plt mice lacking CCR7 ligands. Importantly, systemic application of the CCR7 ligand CCL21 was sufficient to rescue the motility of WT T lymphocytes inside T cell areas of plt/plt recipients. Comparing the movement behavior of T cells in subcapsular areas that are devoid of detectable amounts of CCR7 ligands even in WT mice, we failed to reveal any differences between WT and plt/plt recipients. Furthermore, in both WT and plt/plt recipients, highly motile T cells rapidly accumulated in the subcapsular region after subcutaneous injection of the CCR7 ligand CCL19. Collectively, these data identify CCR7 and its ligands as important chemokinetic factors stimulating the basal motility of CD4+ T cells inside lymph nodes in vivo.
Impaired CD8 T cell memory and CD4 T cell primary responses in IL-7Rα mutant mice
Authors: Osborne Lisa C. , Dhanji Salim , Snow Jonathan W. , Priatel John J. , Ma Melissa C. , Miners M. Jill , Teh Hung-Sia , Goldsmith Mark A. , Abraham Ninan
Published: February 2007

Loss of interleukin (IL)-7 or the IL-7 receptor alpha (IL-7Rα, CD127) results in severe immunodeficiencies in mice and humans. To more precisely identify signals governing IL-7 function in vivo, we have disrupted the IL-7Rα Y449XXM motif in mice by knock-in mutagenesis (IL-7Rα449F). Thymic precursors were reduced in number in IL-7Rα449F mice, but in marked contrast to IL-7Rα−/− knockout mice, thymocytes and peripheral T cells developed normally. Strikingly, Listeria infection revealed that CD4 and CD8 T cells had different requirements for IL-7Rα signals. CD4 T cells failed to mount a primary response, but despite normal CD8 primary responses, maintenance of CD8 memory was impaired in IL-7Rα449F mice. Furthermore, we show that Bcl-2 is IL-7Rα Y449 independent and insufficient for IL-7–mediated maintenance of CD8 memory.
Energy saving through trail following in a marine snail
Authors: Davies Mark S , Blackwell Janine
Published: February 2007

Most snails and slugs locomote over a layer of mucus and although the resultant mucus trail is expensive to produce, we show that this expense can be reduced by trail following. When tracking over fresh conspecific trails, the marine intertidal snailLittorina littorea(L.) produced only approximately 27% of the mucus laid by marker snails. When tracking over weathered trails, snails adjusted their mucus production to recreate a convex trail profile of similar shape and thickness to the trail as originally laid. Maximum energy saving occurs when following recently laid trails which are little weathered. Many and diverse ecological roles for trail following have been proposed. Energy saving is the only role that applies across the Gastropoda and so may help to explain why trail following is such a well-established behaviour.
Analysis of phenotype–genotype connection: the story of dissecting disease pathogenesis in genomic era in China, and beyond
Authors: Shen Yan , Xu Qi , Han Zeguang , Liu Han , Zhou Guang-Biao
Published: February 2007

DNA is the ultimate depository of biological complexity. Thus, in order to understand life and gain insights into disease pathogenesis, genetic information embedded in the sequence of DNA base pairs comprising chromosomes should be deciphered. The stories of investigating the association between phenotype and genotype in China and other countries further demonstrate that genomics can serve as a probe for disease biology. We now know that in Mendelian disorders, one gene is not only a dictator of one phenotype but also a dictator of two or more distinct disorders. Dissecting genetic abnormalities of complex diseases, including diabetes, hypertension, mental diseases, coronary heart disease and cancer, may unravel the complicated networks and crosstalks, and help to simplify the complexity of the disease. The transcriptome and proteomic analysis for medicine not only deepen our understanding of disease pathogenesis, but also provide novel diagnostic and therapeutic strategies. Taken together, genomic research offers a new opportunity for determining how diseases occur, by taking advantage of experiments of nature and a growing array of sophisticated research tools to identify the molecular abnormalities underlying disease processes. We should be ready for the advent of genomic medicine, and put the genome into the doctors' bag, so that we can help patients to conquer diseases.
SARS molecular epidemiology: a Chinese fairy tale of controlling an emerging zoonotic disease in the genomics era
Authors: Zhao Guo-ping
Published: February 2007

Severe acute respiratory syndrome (SARS) was the first natural disaster that challenged the Chinese people at the beginning of the twenty-first century. It was caused by a novel animal coronavirus, never recognized or characterized before. This SARS coronavirus (SARS-CoV) exploited opportunities provided by ‘wet markets’ in southern China to adapt to the palm civet and human. Under the positive selection pressure of human host, certain mutated lineages of the virus became readily transmissible between humans and thus caused the epidemic of 2002–2003. This review will provide first-hand information, particularly from Guangdong, China, about the initial epidemiology, the identification of the aetiological agent of the disease, the molecular evolution study of the virus, the finding of SARS-like CoV in horseshoe bats and the mechanistic analysis for the cross-host tropism transition. The substantial scientific contributions made by the Chinese scientists towards understanding the virus and the disease will be emphasized. Along with the description of the scientific discoveries and analyses, the significant impact of these researches upon the public health measurement or regulations will be highlighted. It is aimed to appreciate the concerted and coordinated global response that controlled SARS within a short period of time as well as the research strategy and methodology developed along with this process, which can be applied in response to other public health challenges, particularly the future emerging/re-merging infectious diseases.
Presence of Lythrum salicaria enhances the bodyguard effects of the parasitoid Asecodes mento for Filipendula ulmaria
Authors: A. Stenberg Johan , Heijari Juha , K. Holopainen Jarmo , Ericson Lars
Published: February 2007

This paper reports significant effects of a co‐occurring plant species (Lythrum salicaria, Lythraceae) on the reproductive success of the perennial herb Filipendula ulmaria (Rosaceae). We studied 15 Filipendula populations in the Skeppsvik Archipelago; seven of which were monospecific and eight mixed with Lythrum. All the Filipendula populations studied harbored the chrysomelid beetle Galerucella tenella, and in 2005 seed set was strongly negatively correlated with the percentage leaf area consumed. Moreover, data from 2004 showed that 25–100% of the G. tenella larvae were parasitized by the hymenopteran parasitoid Asecodes mento, and we found a strong cascading top‐down effect of parasitism in 2004 on Filipendula seed set in 2005. In 2004, parasitism (at the population level) was negatively correlated with percentage leaf area consumed and positively correlated with seed set in 2005. The parasitoid Asecodes also parasitized G. calmariensis, which is monophagous on Lythrum. Mixed populations of Filipendula and Lythrum supported higher densities of their shared ‘bodyguard’Asecodes. Further, Y‐tube bioassays showed that floriferous Filipendula attracted more than twice as many gravid Asecodes females as floriferous Lythrum. Taken together, these findings suggest that coexistence of the two plants results in ‘associational resistance’ for Filipendula and ‘associational susceptibility’ for Lythrum. This scenario was supported for Filipendula since, for this species, we found lower leaf consumption followed by higher seed production in mixed than in monospecific populations. Considered together, our results show that bodyguards may increase the reproductive fitness of a perennial herb, and that the strength of the cascading ‘bodyguard’ effect can be strongly influenced by co‐occurring plants through ‘apparent competition’. This is the first paper to demonstrate that, in the wild, plant species may use odors to compete for ‘bodyguards’, thereby causing asymmetrical ‘apparent competition’ between the herbivores involved. Our data emphasize the need to consider community factors in studies of trophic interactions.
Escaping parasitism in the selfish herd: age, size and density‐dependent warble fly infestation in reindeer
Authors: Fauchald Per , Rødven Rolf , Bårdsen Bård‐Jørgen , Langeland Knut , Tveraa Torkild , Yoccoz Nigel G. , Ims Rolf A.
Published: February 2007

It has been suggested that animals may escape attack from mobile parasites by aggregating in selfish herds. A selfish herd disperses the risk of being attacked among its members and the per individual risk of parasite infection should therefore decrease with increasing animal density through the encounter–dilution effect. Moreover, in a selfish herd, dominant and agile animals should occupy the best positions and thereby receive fewer attacks compared to lower ranked animals at the periphery. We tested these predictions on reindeer (Rangifer tarandus tarandus) parasitized by warble flies (Hypoderma tarandi). Warble flies oviposit their eggs on reindeer during summer and induce strong anti‐parasitic behavioural responses in the herds. In this period, reindeer are sexually segregated; females and calves form large and dense herds while males are more solitary. After hatching, the warble fly larvae migrate under the skin of their host where they encyst. In the present study encysted larvae were counted on newly slaughtered hides of male calves and 1.5 year old males from 18 different reindeer herds in Finnmark, northern Norway with large contrasts in reindeer density. In reindeer, body mass is correlated with fitness and social status and we hypothesized that individual carcass mass reflected the animal's ability to occupy the best positions within the herd. Larval abundance was higher among the 1.5 year old males than among the calves. For calves we found in accordance with the selfish herd hypothesis a negative relationship between larval abundance and animal density and between larval abundance and body mass. These relationships were absent for the 1.5 year old males. We suggest that these differences were due to different grouping behaviour where calves and females, but not males, aggregated in selfish herds where they escaped parasitism.
Effects of large‐scale disturbance on metacommunity structure of terrestrial gastropods: temporal trends in nestedness
Authors: Bloch Christopher P. , Higgins Christopher L. , Willig Michael R.
Published: February 2007

Distributions of species often exhibit nested structure, such that assemblages at species‐poor sites are proper subsets of taxa at more species‐rich sites. Traditionally, this has been viewed as a large‐scale biogeographic pattern and treated implicitly as static from a temporal perspective. Nonetheless, recent work suggests that nestedness may arise at multiple spatio‐temporal scales. A 13‐year data set encompassing the effects of two large‐scale natural disturbances (hurricanes Hugo and Georges) on terrestrial gastropod assemblages was used to test the hypothesis that changes in species composition resulting from disturbance alter the degree of nestedness exhibited over time at two spatial scales. Gastropod assemblages were least nested immediately following disturbance, and nestedness increased thereafter. Although land‐use history influenced the degree of nestedness, trajectories of nestedness following disturbance were similar irrespective of disturbance history or hurricane identity. The effects of hurricanes with respect to nestedness of terrestrial gastropods may be general and predictable, even though species respond to hurricanes in disparate fashions. By damaging some localities within the forest more severely than others, a hurricane dismantles extant patterns of species composition and severs connections among sites, as inhospitable microclimatic conditions limit dispersal of gastropods. As time passes and the forest canopy regenerates, conditions ameliorate, and movement among sites becomes more frequent. Thus, a conclusion based on a single time period may not characterize the study system in general. Consequently, explanations for nested structure that incorporate variability in ecological as well as evolutionary time will improve the applicability and comparability of nested subsets analysis across study systems.
Plant–herbivore interactions in Alaskan arctic tundra change with soil nutrient availability
Authors: Gough Laura , Ramsey Elizabeth A. , Johnson David R.
Published: February 2007

Herbivores in nutrient‐limited systems such as arctic tundra have been suggested to play a minor role in controlling plant growth simply because they are relatively few in number. However, theory predicts that as net primary productivity (NPP) increases because of greater inputs of nutrients or energy, herbivores may have greater effects on plant growth. This prediction has not been tested in the context of climate warming in arctic tundra, which may increase soil nutrient availability and thus NPP. We examined a long‐term experiment that excluded small and large mammalian herbivores and increased soil nutrients in two arctic Alaskan tundra communities: dry heath (DH) and moist acidic tussock (MAT). In the ninth year of manipulations, we measured weekly growth of three plant species of three growth forms: tussock‐forming graminoid, rhizomatous graminoid, and dwarf deciduous shrub, in each community. All species grew better when fertilized. In DH, this increase in growth was exaggerated when plants were protected from herbivores, confirming that herbivory had a negative effect on plant growth under increased nutrient conditions, but was unimportant under ambient soil conditions. However, in MAT, the importance of herbivory differed among species with fertilization. The tussock‐forming sedge at MAT, Eriophorum vaginatum, grew better and flowered more when fenced under both ambient and amended nutrients compared to plants exposed to herbivores. This species decreases in abundance in long‐term fertilized plots when mammals are present, and our results suggest that herbivory may be accounting for at least some of that loss, in addition to shifts in competitive relationships. Although we only focused on individual plants here rather than the entire community, our results suggest that under the increased soil nutrient conditions expected with continued climate warming in the Arctic, herbivores may become more important in affecting several abundant tundra plant populations, and should not be ignored.
Root herbivores influence the behaviour of an aboveground parasitoid through changes in plant‐volatile signals
Authors: Soler Roxina , Harvey Jeffrey A. , Kamp Andre F. D. , Vet Louise E. M. , Van der Putten Wim H. , Van Dam Nicole M. , Stuefer Josef F. , Gols Rieta , Hordijk Cornelis A. , Martijn Bezemer T.
Published: February 2007

It is widely reported that plants emit volatile compounds when they are attacked by herbivorous insects, which may be used by parasitoids and predators to locate their host or prey. The study of herbivore‐induced plant volatiles and their role in mediating interactions between plants, herbivores and their natural enemies have been primarily based on aboveground systems, generally ignoring the potential interactions between above and belowground infochemical‐ and food webs. This study examines whether herbivory by Delia radicum feeding on roots of Brassica nigra (black mustard) affects the behaviour of Cotesia glomerata, a parasitoid of the leaf herbivore Pieris brassicae, mediated by changes in plant volatiles. In a semi‐field experiment with root‐damaged and root‐undamaged plants C. glomerata prefers to oviposit in hosts feeding on root‐undamaged plants. In addition, in a flight‐cage experiment the parasitoid also prefers to search for hosts on plants without root herbivores. Plants exposed to root herbivory were shown to emit a volatile blend characterized by high levels of specific sulphur volatile compounds, which are reported to be highly toxic for insects, combined with low levels of several compounds, i.e. beta‐farnesene, reported to act as attractants for herbivorous and carnivorous insects. Our results provide evidence that the foraging behaviour of a parasitoid of an aboveground herbivore can be influenced by belowground herbivores through changes in the plant volatile blend. Such indirect interactions may have profound consequences for the evolution of host selection behaviour in parasitoids, and may play an important role in the structuring and functioning of communities.
The evolution of crypsis in replicating populations of web‐based prey
Authors: Sherratt Thomas N. , Pollitt David , Wilkinson David M.
Published: February 2007

To investigate the evolution of background matching (crypsis) when prey are viewed against uniform and heterogeneous (alternating) backgrounds, we conducted some web‐based experiments. Visitors to our experimental web site were rewarded for finding artificial prey, thereby providing a measure of their detectability. We first compared the “survivorship” of a range of pixilated prey phenotypes presented against both light green and dark green pixilated backgrounds and found clear evidence for a concave tradeoff curve, indicating that specialism on one or the other background would maximise their overall survivorship. We then compared the survivorship of a range of spotted prey phenotypes presented against backgrounds with small spots and large spots and found evidence for a more linear tradeoff curve, indicating that both intermediates and specialists would have approximately equal survivorship. Replicated evolutionary experiments were then conducted in which the survivors in any given system automatically reproduced themselves (subject to occasional mutation) when their population size was depleted to a critical threshold. Here close background matching readily evolved when prey were presented against a single uniform pixilated environment and when prey were presented against a single uniform spotted environment. As expected, the background matching that evolved in alternating light and dark green environments involved specialism on one or other background, and no intermediate forms evolved. By contrast, a more polymorphic range of phenotypes evolved in the alternating small and large spotted environments. To our knowledge this is the first time that automatically regenerating populations of web based prey have been set up to address evolutionary questions. Our findings have clearly shown conditions under which jack‐of‐all‐trades cryptic forms survive poorly, and, although more work is needed, it may also help explain why background matching frequently appears so specialized in natural systems.
Methamphetamine use and infectious disease‐related behaviors in men who have sex with men: implications for interventions
Authors: Shoptaw Steven , Reback Cathy J.
Published: February 2007

Aims  Review the current evidence regarding the prevalence of methamphetamine use among men who have sex with men (MSM) and to evaluate the factors that contribute to methamphetamine use and potential for sexual transmission of HIV and other infectious diseases.

Methods  Databased reports address (1) epidemiology of methamphetamine use in MSM; (2) methamphetamine use and risk behaviors for sexually transmitted infections; and (3) interventions.

Findings  Methamphetamine use is highly prevalent in MSM. Strong associations between methamphetamine use and HIV‐related sexual transmission behaviors are noted across studies of MSM and correspond to increased incidence for HIV and syphilis compared to MSM who do not use the drug. Behavioral treatments produce sustained reductions in methamphetamine use and concomitant sexual risk behaviors among methamphetamine‐dependent MSM.

Conclusions  Brief screening of methamphetamine use for MSM who seek physical, mental health and substance abuse services is recommended. Behavioral interventions that address methamphetamine use may range from brief interventions to intensive out‐patient treatments.
Electrocardiographic abnormalities in methamphetamine abusers
Authors: Haning William , Goebert Deborah
Published: February 2007

Aims  Although many adverse cardiovascular outcomes are mentioned in conjunction with methamphetamine use, a causal relationship between methamphetamine use and arrhythmia or cardiomyopathy has not been demonstrated in man. Clinical experience with methamphetamine users suggested a higher incidence of electrocardiographic abnormalities. This study seeks to quantify that incidence, among subjects enrolled in a study of adults with methamphetamine dependence.

Methods  Electrocardiograms obtained during screening in a previous clinical trial were examined. The study population (n = 158) of adults with methamphetamine dependence [Diagnostic and Statistical Manual version IV (DSM IV‐TR)] was drawn from five sites across the United States, recruited in the interval 2002–03.

Results  A significant variance from the normal population was noted in the electrocardiograms of the study cohort. Among the abnormalities was a prolongation of the QTc beyond 440 ms in 27.2% of the group. QTc prolongation to this extent poses a particular risk for ventricular arrhythmias, most notably torsades de pointes.

Conclusions  We believe that this is the first demonstration of clinically significant QTc prolongation in a methamphetamine‐using population, and that this has implications for the types of arrhythmias for which this population is at risk. It may further provide a marker for risk of cardiomyopathy. The fact of electrocardiographic changes with potential cardiac risks may be useful in a motivational interviewing approach, in challenging the methamphetamine user's basis for continuing use.
Why do we need an Addiction supplement focused on methamphetamine?
Authors: Rawson Richard A. , Condon Timothy P.
Published: February 2007

Methamphetamine is a substantial public health problem in many communities in the United States and in other parts of the world. In order to bring new knowledge about methamphetamine to policy makers, clinicians and researchers, this volume has compiled a set of articles containing new information about the drug and its effects. The articles contain information presented by researchers at two special methamphetamine meetings sponsored by the National Institute on Drug Abuse in 2005.
Structural and metabolic brain changes in the striatum associated with methamphetamine abuse
Authors: Chang Linda , Alicata Daniel , Ernst Thomas , Volkow Nora
Published: February 2007

Aims  To review structural, chemical and metabolic brain changes, particularly those in the basal ganglia, in individuals who used methamphetamine, as well as in children with prenatal methamphetamine exposure.

Methods  Magnetic resonance imaging (MRI) and positron emission tomography (PET) studies that evaluated brain structural, chemical and metabolite changes in methamphetamine subjects, or children with prenatal methamphetamine exposure, were reviewed and summarized. Relevant pre‐clinical studies that provided insights to the interpretations of these imaging studies were also reviewed.

Results  In adults who used methamphetamine, MRI demonstrates enlarged striatal volumes, while MR spectroscopy shows reduced concentrations of the neuronal marker N‐acetylasparate and total creatine in the basal ganglia. In contrast, children with prenatal methamphetamine exposure show smaller striatal structures and elevated total creatine. Furthermore, PET studies consistently showed reduced dopamine transporter (DAT) density and reduced dopamine D2 receptors in the striatum of methamphetamine subjects. PET studies also found lower levels of serotonergic transporter density and vesicular monoamine transporter (VMAT2) across striatal subregions, as well as altered brain glucose metabolism that correlated with severity of psychiatric symptoms in the limbic and orbitofrontal regions.

Conclusion  Neuroimaging studies demonstrate abnormalities in brain structure and chemistry convincingly in individuals who used methamphetamine and in children with prenatal methamphetamine exposure, especially in the striatum. However, many important questions remain and larger sample sizes are needed to validate these preliminary observations. Furthermore, longitudinal studies are needed to evaluate the effects of treatment and abstinence on these brain changes and to determine whether imaging, and possibly genetic, markers can be used to predict treatment outcome or relapse.
Predicting in‐treatment performance and post‐treatment outcomes in methamphetamine users
Authors: Hillhouse Maureen P. , Marinelli‐Casey Patricia , Gonzales Rachel , Ang Alfonso , Rawson Richard A. ,   the Methamphetamine Treatment Project Corporate Authors
Published: February 2007

Aims  This study examines the utility of individual drug use and treatment characteristics for predicting in‐treatment performance and post‐treatment outcomes over a 1‐year period.

Design, setting and participants  Data were collected from 420 adults who participated in the Methamphetamine Treatment Project (MTP), a multi‐site study of randomly assigned treatment for methamphetamine dependence. Interviews were conducted at baseline, during treatment and during three follow‐up time‐points: treatment discharge and at 6 and 12 months following admission.

Measurements  The Addiction Severity Index (ASI); the Craving, Frequency, Intensity and Duration Estimate (CFIDE); and laboratory urinalysis results were used in the current study.

Findings  Analyses addressed both in‐treatment performance and post‐treatment outcomes. The most consistent finding is that pre‐treatment methamphetamine use predicts in‐treatment performance and post‐treatment outcomes. No one variable predicted all in‐treatment performance measures; however, gender, route of administration and pre‐treatment methamphetamine use were significant predictors. Similarly, post‐treatment outcomes were predicted by a range of variables, although pre‐treatment methamphetamine use was significantly associated with each post‐treatment outcome.

Conclusions  These findings provide useful empirical information about treatment outcomes for methamphetamine abusers, and highlight the utility of assessing individual and in‐treatment characteristics in the development of appropriate treatment plans.
SHORT COMMUNICATION: Associations of BF2 alleles with antibody titres and production traits in commercial pure line broiler chickens
Authors: Ewald S. J. , Ye X. , Avendano S. , McLeod S. , Lamont S. J. , Dekkers J. C. M.
Published: February 2007

Three commercial broiler pure lines were evaluated for associations of sire BF2 (major histocompatibility complex class I) alleles with progeny phenotypic traits. Significant BF2 associations with a subset of traits were observed in two lines. The BF2*21 allele was positively associated with antibody titre to infectious bursal disease virus in both lines. Other associations were line‐specific.