bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling the resonant release of synaptic transmitter by hair cells as an example of biological oscillators with cooperative steps
Authors: Andor-Ardó Daniel , Hudspeth A. J. , Magnasco Marcelo O. , Piro Oreste
Published: January 2010

The initial synapses of the auditory system, which connect hair cells to afferent nerve fibers, display two unusual features. First, synaptic transmission occurs in a multiquantal fashion: the contents of multiple synaptic vesicles are discharged simultaneously. Second, synaptic transmission may be tuned to specific frequencies of stimulation. We developed a minimal theoretical model to explore the possibility that hair-cell synapses achieve both multiquantal release and frequency selectivity through a cooperative mechanism for the exocytotic release of neurotransmitter. We first characterized vesicle release as a four-step cycle at each release site, then generalized the result to an arbitrary number of steps. The cyclic process itself induces some degree of resonance, and may display a stable, underdamped fixed point of the release dynamics associated with a pair of complex eigenvalues. Cooperativity greatly enhances the frequency selectivity by moving the eigenvalues toward the imaginary axis; spontaneously oscillatory release can arise beyond a Hopf bifurcation. These phenomena occur both in the macroscopic limit, when the number of release sites involved is very large, and in the more realistic stochastic regime, when only a limited number of release sites participate at each synapse. It is thus possible to connect multiquantal release with frequency selectivity through the mechanism of cooperativity.
Design, Development and Control of a Hopping Machine – an Exercise in Biomechatronics
Authors: Naik Kuldip , Mehrandezh Mehran , Barden John
Published: January 2010

Hopping is a complicated dynamic behaviour in the animal kingdom. Development of a hopping machine that can mimic the biomechanics of jumping in Homo sapiens is envisioned. In this context, the design, development and control of a cost‐effective, pneumatically actuated, one‐legged hopping machine were initiated at the University ofRegina in 2005. The pneumatic actuator has a simple design that employs an off‐the‐shelf on/off control valve which regulates the air pressure supplied to the hopper′s body using a pulse width modulated (PWM) signal. The objective is to maintain a constant jumping height in the hopper after going through a finite number of hopping cycles. The mechanistic model of the system was investigated in full detail. This model facilitates: (1) the design of the actuating system, and (2) the synthesis and verification of different control strategies in a simulation environment prior to implementation in the real world. The movement of the hopper is supported by a vertical slide; therefore, the hopper can only jump in place. However, the proposed control strategy and the propulsion unit can be further utilised for stable hopping in a 3‐D environment. A model‐free Neuro‐PD controller was then designed, trained and implemented on a real system. Simulation and experimentation showed promising results. This system can be used as an educational tool for teaching real‐time control of hybrid and non‐linear systems. It can be also used as a biomechatronics test bed to simulate the effect of different timings in firing action potentials in jump‐causing leg muscles on achieving a desired jumping height in the animal kingdom.
Type I interferon signaling in hematopoietic cells is required for survival in mouse polymicrobial sepsis by regulating CXCL10
Authors: Kelly-Scumpia Kindra M. , Scumpia Philip O. , Delano Matthew J. , Weinstein Jason S. , Cuenca Alex G. , Wynn James L. , Moldawer Lyle L.
Published: January 2010

Type I interferon (IFN) α/β is critical for host defense. During endotoxicosis or highly lethal bacterial infections where systemic inflammation predominates, mice deficient in IFN-α/β receptor (IFNAR) display decreased systemic inflammation and improved outcome. However, human sepsis mortality often occurs during a prolonged period of immunosuppression and not from exaggerated inflammation. We used a low lethality cecal ligation and puncture (CLP) model of sepsis to determine the role of type I IFNs in host defense during sepsis. Despite increased endotoxin resistance, IFNAR−/− and chimeric mice lacking IFNAR in hematopoietic cells display increased mortality to CLP. This was not associated with an altered early systemic inflammatory response, except for decreased CXCL10 production. IFNAR−/− mice display persistently elevated peritoneal bacterial counts compared with wild-type mice, reduced peritoneal neutrophil recruitment, and recruitment of neutrophils with poor phagocytic function despite normal to enhanced adaptive immune function during sepsis. Importantly, CXCL10 treatment of IFNAR−/− mice improves survival and decreases peritoneal bacterial loads, and CXCL10 increases mouse and human neutrophil phagocytosis. Using a low lethality sepsis model, we identify a critical role of type I IFN–dependent CXCL10 in host defense during polymicrobial sepsis by increasing neutrophil recruitment and function.
Plasma effects in a travelling wave tube
Authors: Kumar Manish , Bhasin Lalita , Tripathi V K
Published: January 2010

The effect of a plasma on a travelling wave tube comprising a sheath helix is studied. The plasma, taken to be (i) strongly magnetized or (ii) unmagnetized, allows a larger beam current to pass owing to charge and current neutralization. The beam excites an azimuthally symmetric slow wave via Cerenkov resonance. In the case of a strongly magnetized plasma when ωp>ω (where ωp is the plasma frequency), the amplitude of the axial electric field peaks on the axis and the phase velocity is suppressed, whereas for ωp<ω the field amplitude peaks at the helix surface and the phase velocity is enhanced. As a consequence, when a beam is placed close to the helix, the growth rate increases with ωp as long as ωp <ω and decreases with ωp when ωp>ω. In the case of an unmagnetized plasma, the mode is more strongly localized near the helix and the growth rate increases with ωp.
Product operator descriptions of the 2D DEPT J-resolved NMR experiment for weakly coupled ISn (, ; n=1, 2, 3) spin systems
Authors: Tokatlı Ahmet , Bahçeli Semiha
Published: January 2010

There are a variety of multi-pulse nuclear magnetic resonance (NMR) experiments for spectral assignment of complex molecules in a solution. The two-dimensional (2D) distortionless enhancement by polarization transfer (DEPT) J-resolved NMR experiment is a 13C-detected, spectral editing polarization transfer technique. The product operator theory is widely used for an analytical description of the multi-pulse NMR experiment for weakly coupled spin systems. In this study, analytical descriptions of the 2D DEPT J-resolved NMR experiment for weakly coupled IS

n
(, ; n=1, 2, 3) spin systems using the product operator theory have been introduced for the first time. The calculated intensities and positions of the observable signals are simulated for molecules containing [13C , 81Br )] nuclei by using a MAPLE program on a computer. Finally, we present a theoretical discussion and experimental suggestions.
Mutations inCaenorhabditis elegans him-19Show Meiotic Defects That Worsen with Age
Authors: Tang Lois , Machacek Thomas , Mamnun Yasmine M. , Penkner Alexandra , Gloggnitzer Jiradet , Wegrostek Christina , Konrat Robert , Jantsch Michael F. , Loidl Josef , Jantsch Verena
Published: January 2010

From a screen for meiotic Caenorhabditis elegans mutants based on high incidence of males, we identified a novel gene, him-19, with multiple functions in prophase of meiosis I. Mutant him-19(jf6) animals show a reduction in pairing of homologous chromosomes and subsequent bivalent formation. Consistently, synaptonemal complex formation is spatially restricted and possibly involves nonhomologous chromosomes. Also, foci of the recombination protein RAD-51 occur delayed or cease altogether. Ultimately, mutation of him-19 leads to chromosome missegregation and reduced offspring viability. The observed defects suggest that HIM-19 is important for both homology recognition and formation of meiotic DNA double-strand breaks. It therefore seems to be engaged in an early meiotic event, resembling in this respect the regulator kinase CHK-2. Most astonishingly, him-19(jf6) hermaphrodites display worsening of phenotypes with increasing age, whereas defects are more severe in female than in male meiosis. This finding is consistent with depletion of a him-19-dependent factor during the production of oocytes. Further characterization of him-19 could contribute to our understanding of age-dependent meiotic defects in humans.
BamView: viewing mapped read alignment data in the context of the reference sequence
Authors: Carver Tim , Böhme Ulrike , Otto Thomas D. , Parkhill Julian , Berriman Matthew
Published: January 2010

Summary: BamView is an interactive Java application for visualizing the large amounts of data stored for sequence reads which are aligned against a reference genome sequence. It supports the BAM (Binary Alignment/Map) format. It can be used in a number of contexts including SNP calling and structural annotation. BamView has also been integrated into Artemis so that the reads can be viewed in the context of the nucleotide sequence and genomic features.

Availability: BamView and Artemis are freely available (under a GPL licence) for download (for MacOSX, UNIX and Windows) at: http://bamview.sourceforge.net/

Contact:  artemis@sanger.ac.uk
Biophysics of magnetic orientation: strengthening the interface between theory and experimental design
Authors: Kirschvink Joseph L. , Winklhofer Michael , Walker Michael M.
Published: January 2010

The first demonstrations of magnetic effects on the behaviour of migratory birds and homing pigeons in laboratory and field experiments, respectively, provided evidence for the longstanding hypothesis that animals such as birds that migrate and home over long distances would benefit from possession of a magnetic sense. Subsequent identification of at least two plausible biophysical mechanisms for magnetoreception in animals, one based on biogenic magnetite and another on radical-pair biochemical reactions, led to major efforts over recent decades to test predictions of the two models, as well as efforts to understand the ultrastructure and function of the possible magnetoreceptor cells. Unfortunately, progress in understanding the magnetic sense has been challenged by: (i) the availability of a relatively small number of techniques for analysing behavioural responses to magnetic fields by animals; (ii) difficulty in achieving reproducible results using the techniques; and (iii) difficulty in development and implementation of new techniques that might bring greater experimental power. As a consequence, laboratory and field techniques used to study the magnetic sense today remain substantially unchanged, despite the huge developments in technology and instrumentation since the techniques were developed in the 1950s. New methods developed for behavioural study of the magnetic sense over the last 30 years include the use of laboratory conditioning techniques and tracking devices based on transmission of radio signals to and from satellites. Here we consider methodological developments in the study of the magnetic sense and present suggestions for increasing the reproducibility and ease of interpretation of experimental studies. We recommend that future experiments invest more effort in automating control of experiments and data capture, control of stimulation and full blinding of experiments in the rare cases where automation is impossible. We also propose new experiments to confirm whether or not animals can detect magnetic fields using the radical-pair effect together with an alternate hypothesis that may explain the dependence on light of responses by animals to magnetic field stimuli.
On second-order differential equations with highly oscillatory forcing terms
Authors: Condon Marissa , Deaño Alfredo , Iserles Arieh
Published: January 2010

We present a method to compute efficiently solutions of systems of ordinary differential equations (ODEs) that possess highly oscillatory forcing terms. This approach is based on asymptotic expansions in inverse powers of the oscillatory parameter, and features two fundamental advantages with respect to standard numerical ODE solvers: first, the construction of the numerical solution is more efficient when the system is highly oscillatory, and, second, the cost of the computation is essentially independent of the oscillatory parameter. Numerical examples are provided, featuring the Van der Pol and Duffing oscillators and motivated by problems in electronic engineering.
Modelling bacterial behaviour close to a no-slip plane boundary: the influence of bacterial geometry
Authors: Shum H. , Gaffney E. A. , Smith D. J.
Published: January 2010

We describe a boundary-element method used to model the hydrodynamics of a bacterium propelled by a single helical flagellum. Using this model, we optimize the power efficiency of swimming with respect to cell body and flagellum geometrical parameters, and find that optima for swimming in unbounded fluid and near a no-slip plane boundary are nearly indistinguishable. We also consider the novel optimization objective of torque efficiency and find a very different optimal shape. Excluding effects such as Brownian motion and electrostatic interactions, it is demonstrated that hydrodynamic forces may trap the bacterium in a stable, circular orbit near the boundary, leading to the empirically observable surface accumulation of bacteria. Furthermore, the details and even the existence of this stable orbit depend on geometrical parameters of the bacterium, as described in this article. These results shed some light on the phenomenon of surface accumulation of micro-organisms and offer hydrodynamic explanations as to why some bacteria may accumulate more readily than others based on morphology.
Ions first: Na+uptake shifts from the skin to the gills before O2uptake in developing rainbow trout,Oncorhynchus mykiss
Authors: Fu Clarice , Wilson Jonathan M. , Rombough Peter J. , Brauner Colin J.
Published: January 2010

This is the first direct physiological evidence in support of the ionoregulatory hypothesis, challenging the long-held assumption that teleost gills develop initially for gas exchange. Resting unidirectional sodium (Na+) uptake and oxygen (O2) uptake across the skin and gills were measured simultaneously in larval rainbow trout,Oncorhynchus mykiss, during development. In soft and hard water, Na+uptake shifted to the gills by 15 and 16 days post-hatch (dph) while O2uptake took 50–80% longer and shifted by 23 and 28 dph, respectively. This suggests that gills are required for ionoregulation prior to gas exchange in developing rainbow trout. The age of transition for Na+uptake, gill Na+, K+-ATPase (NKA) α-subunit protein expression and gill NKA enzyme activity were not significantly different between soft and hard water-reared groups, which suggests a lack of plasticity in gill ionoregulatory development.

In rainbow trout, the gills assume a dominant role in ionoregulation before gas exchange, suggesting that ionoregulation may be the initial driving force for gill development. Further investigation is required to determine whether this pattern is consistent with other teleosts and more basal fishes during early development to gain insight into the role of ionoregulation in vertebrate gill evolution.
Developmental palaeontology in synapsids: the fossil record of ontogeny in mammals and their closest relatives
Authors: Sánchez-Villagra Marcelo R.
Published: January 2010

The study of fossilized ontogenies in mammals is mostly restricted to postnatal and late stages of growth, but nevertheless can deliver great insights into life history and evolutionary mechanisms affecting all aspects of development. Fossils provide evidence of developmental plasticity determined by ecological factors, as when allometric relations are modified in species which invaded a new space with a very different selection regime. This is the case of dwarfing and gigantism evolution in islands. Skeletochronological studies are restricted to the examination of growth marks mostly in the cement and dentine of teeth and can provide absolute age estimates. These, together with dental replacement data considered in a phylogenetic context, provide life-history information such as maturation time and longevity. Palaeohistology and dental replacement data document the more or less gradual but also convergent evolution of mammalian growth features during early synapsid evolution. Adult phenotypes of extinct mammals can inform developmental processes by showing a combination of features or levels of integration unrecorded in living species. Some adult features such as vertebral number, easily recorded in fossils, provide indirect information about somitogenesis and hox-gene expression boundaries. Developmental palaeontology is relevant for the discourse of ecological developmental biology, an area of research where features of growth and variation are fundamental and accessible among fossil mammals.
Induced niche shift as an anti-predator response for an endoparasitoid
Authors: Muratori Frédéric B. , Borlee Sophie , Messing Russell H.
Published: January 2010

When two developmental stages do not share the same ecological niche, the control of the niche shift through a change in developmental timing, referred to as ‘heterokairy’, can provide an adaptive advantage for the individual (e.g. if mortality risk is higher in the first niche). For endoparasitic species that develop inside another (host) species, mortality of the host may directly induce mortality risk for the parasite. Thus, endoparasitoid larvae should be selected for response to host predation. In this study, aphids previously parasitized by the endoparasitoid
Endaphis fugitiva
, Gagné and Muratori (Diptera: Cecidomyiidae), were experimentally exposed to increased mortality risks. Both simulated attack and actual predator attacks against aphid hosts induced early emergence of the parasitoid larvae. Parasitoid emergence from the aphids occurred several minutes before the predator finished feeding on the aphid, allowing enough time for the parasitoid larvae to avoid direct predation. Predator-induced emergence produced significantly smaller parasitoid larvae than controls, but, interestingly, no effect on Endaphis adult size was found. To our knowledge, this is the first evidence of induced emergence in an insect parasitoid, but we suggest that this mechanism might be at work in many other species where plasticity in development time allows the individual to perform an adaptive niche shift.
Give us the tools and we will do the job: symbiotic bacteria affect olive fly fitness in a diet-dependent fashion
Authors: Ben-Yosef Michael , Aharon Yael , Jurkevitch Edouard , Yuval Boaz
Published: January 2010

Olive flies (
Bactrocera oleae
) are intimately associated with bacteria throughout their life cycle, and both larvae and adults are morphologically adapted for housing bacteria in the digestive tract. We tested the hypothesis that these bacteria contribute to the adult fly's fitness in a diet-dependent fashion. We predicted that when dietary protein is superabundant, bacterial contribution will be minimal. Conversely, in the absence of protein, or when only non-essential amino acids are present (as in the fly's natural diet), we predicted that bacterial contribution to fitness will be significant. Accordingly, we manipulated diet and the presence of bacteria in female olive flies, and monitored fecundity—an indirect measure of fitness. Bacteria did not affect fecundity when females were fed a nutritionally poor diet of sucrose, or a protein-rich, nutritionally complete diet. However, when females were fed a diet containing non-essential amino acids as the sole source of amino nitrogen, egg production was significantly enhanced in the presence of bacteria. These results suggest that bacteria were able to compensate for the skewed amino acid composition of the diet and may be indispensable for wild adult olive flies that subsist mainly on nitrogen-poor resources such as honeydew.
Personality traits and dispersal tendency in the invasive mosquitofish (Gambusia affinis)
Authors: Cote Julien , Fogarty Sean , Weinersmith Kelly , Brodin Tomas , Sih Andrew
Published: January 2010

Ecological invasions, where non-native species spread to new areas, grow to high densities and have large, negative impacts on ecological communities, are a major worldwide problem. Recent studies suggest that one of the key mechanisms influencing invasion dynamics is personality-dependent dispersal: the tendency for dispersers to have a different personality type than the average from a source population. We examined this possibility in the invasive mosquitofish (Gambusia affinis). We measured individual tendencies to disperse in experimental streams and several personality traits: sociability, boldness, activity and exploration tendency before and three weeks after dispersal. We found that mosquitofish display consistent behavioural tendencies over time, and significant positive correlations between all personality traits. Most notably, sociability was an important indicator of dispersal distance, with more asocial individuals dispersing further, suggesting personality-biased dispersal on an invasion front. These results could have important ecological implications, as invasion by a biased subset of individuals is likely to have different ecological impacts than invasion by a random group of colonists.
Host sanctions and pollinator cheating in the fig tree–fig wasp mutualism
Authors: Jandér K. Charlotte , Herre Edward Allen
Published: January 2010

Theory predicts that mutualisms should be vulnerable to invasion by cheaters, yet mutualistic interactions are both ancient and diverse. What prevents one partner from reaping the benefits of the interaction without paying the costs? Using field experiments and observations, we examined factors affecting mutualism stability in six fig tree–fig wasp species pairs. We experimentally compared the fitness of wasps that did or did not perform their most basic mutualistic service, pollination. We found host sanctions that reduced the fitness of non-pollinating wasps in all derived, actively pollinated fig species (where wasps expend time and energy pollinating), but not in the basal, passively pollinated fig species (where wasps do not). We further screened natural populations of pollinators for wasp individuals that did not carry pollen (‘cheaters’). Pollen-free wasps occurred only in actively pollinating wasp species, and their prevalence was negatively correlated with the sanction strength of their host species. Combined with previous studies, our findings suggest that (i) mutualisms can show coevolutionary dynamics analogous to those of ‘arms races’ in overtly antagonistic interactions; (ii) sanctions are critical for long-term mutualism stability when providing benefits to a host is costly, and (iii) there are general principles that help maintain cooperation both within and among species.
Linking species abundance distributions in numerical abundance and biomass through simple assumptions about community structure
Authors: Henderson Peter A. , Magurran Anne E.
Published: January 2010

Species abundance distributions (SADs) are widely used as a tool for summarizing ecological communities but may have different shapes, depending on the currency used to measure species importance. We develop a simple plotting method that links SADs in the alternative currencies of numerical abundance and biomass and is underpinned by testable predictions about how organisms occupy physical space. When log numerical abundance is plotted against log biomass, the species lie within an approximately triangular region. Simple energetic and sampling constraints explain the triangular form. The dispersion of species within this triangle is the key to understanding why SADs of numerical abundance and biomass can differ. Given regular or random species dispersion, we can predict the shape of the SAD for both currencies under a variety of sampling regimes. We argue that this dispersion pattern will lie between regular and random for the following reasons. First, regular dispersion patterns will result if communities are comprised groups of organisms that use different components of the physical space (e.g. open water, the sea bed surface or rock crevices in a marine fish assemblage), and if the abundance of species in each of these spatial guilds is linked to the way individuals of varying size use the habitat. Second, temporal variation in abundance and sampling error will tend to randomize this regular pattern. Data from two intensively studied marine ecosystems offer empirical support for these predictions. Our approach also has application in environmental monitoring and the recognition of anthropogenic disturbance, which may change the shape of the triangular region by, for example, the loss of large body size top predators that occur at low abundance.
Maturation Stress Generation in Poplar Tension Wood Studied by Synchrotron Radiation Microdiffraction
Authors: Clair Bruno , Alméras Tancrède , Pilate Gilles , Jullien Delphine , Sugiyama Junji , Riekel Christian
Published: January 2010

Tension wood is widespread in the organs of woody plants. During its formation, it generates a large tensile mechanical stress, called maturation stress. Maturation stress performs essential biomechanical functions such as optimizing the mechanical resistance of the stem, performing adaptive movements, and ensuring long-term stability of growing plants. Although various hypotheses have recently been proposed, the mechanism generating maturation stress is not yet fully understood. In order to discriminate between these hypotheses, we investigated structural changes in cellulose microfibrils along sequences of xylem cell differentiation in tension and normal wood of poplar (Populusdeltoides × Populustrichocarpa ‘I45-51’). Synchrotron radiation microdiffraction was used to measure the evolution of the angle and lattice spacing of crystalline cellulose associated with the deposition of successive cell wall layers. Profiles of normal and tension wood were very similar in early development stages corresponding to the formation of the S1 and the outer part of the S2 layer. The microfibril angle in the S2 layer was found to be lower in its inner part than in its outer part, especially in tension wood. In tension wood only, this decrease occurred together with an increase in cellulose lattice spacing, and this happened before the G-layer was visible. The relative increase in lattice spacing was found close to the usual value of maturation strains, strongly suggesting that microfibrils of this layer are put into tension and contribute to the generation of maturation stress.
The Arabidopsis PHYTOCHROME KINASE SUBSTRATE2 Protein Is a Phototropin Signaling Element That Regulates Leaf Flattening and Leaf Positioning
Authors: de Carbonnel Matthieu , Davis Phillip , Roelfsema M. Rob G. , Inoue Shin-ichiro , Schepens Isabelle , Lariguet Patricia , Geisler Markus , Shimazaki Ken-ichiro , Hangarter Roger , Fankhauser Christian
Published: January 2010

In Arabidopsis (Arabidopsis thaliana), the blue light photoreceptor phototropins (phot1 and phot2) fine-tune the photosynthetic status of the plant by controlling several important adaptive processes in response to environmental light variations. These processes include stem and petiole phototropism (leaf positioning), leaf flattening, stomatal opening, and chloroplast movements. The PHYTOCHROME KINASE SUBSTRATE (PKS) protein family comprises four members in Arabidopsis (PKS1–PKS4). PKS1 is a novel phot1 signaling element during phototropism, as it interacts with phot1 and the important signaling element NONPHOTOTROPIC HYPOCOTYL3 (NPH3) and is required for normal phot1-mediated phototropism. In this study, we have analyzed more globally the role of three PKS members (PKS1, PKS2, and PKS4). Systematic analysis of mutants reveals that PKS2 (and to a lesser extent PKS1) act in the same subset of phototropin-controlled responses as NPH3, namely leaf flattening and positioning. PKS1, PKS2, and NPH3 coimmunoprecipitate with both phot1-green fluorescent protein and phot2-green fluorescent protein in leaf extracts. Genetic experiments position PKS2 within phot1 and phot2 pathways controlling leaf positioning and leaf flattening, respectively. NPH3 can act in both phot1 and phot2 pathways, and synergistic interactions observed between pks2 and nph3 mutants suggest complementary roles of PKS2 and NPH3 during phototropin signaling. Finally, several observations further suggest that PKS2 may regulate leaf flattening and positioning by controlling auxin homeostasis. Together with previous findings, our results indicate that the PKS proteins represent an important family of phototropin signaling proteins.
Combined Bimolecular Fluorescence Complementation and Förster Resonance Energy Transfer Reveals Ternary SNARE Complex Formation in Living Plant Cells
Authors: Kwaaitaal Mark , Keinath Nana F. , Pajonk Simone , Biskup Christoph , Panstruga Ralph
Published: January 2010

Various fluorophore-based microscopic methods, comprising Förster resonance energy transfer (FRET) and bimolecular fluorescence complementation (BiFC), are suitable to study pairwise interactions of proteins in living cells. The analysis of interactions between more than two protein partners using these methods, however, remains difficult. In this study, we report the successful application of combined BiFC-FRET-fluorescence lifetime imaging microscopy and BiFC-FRET-acceptor photobleaching measurements to visualize the formation of ternary soluble N-ethylmaleimide-sensitive factor attachment receptor complexes in leaf epidermal cells. This method expands the repertoire of techniques to study protein-protein interactions in living plant cells by a procedure capable of visualizing simultaneously interactions between three fluorophore-tagged polypeptide partners.
The Arabidopsis Prohibitin Gene PHB3 Functions in Nitric Oxide–Mediated Responses and in Hydrogen Peroxide–Induced Nitric Oxide Accumulation
Authors: Wang Yong , Ries Amber , Wu Kati , Yang Albert , Crawford Nigel M.
Published: January 2010

To discover genes involved in nitric oxide (NO) metabolism, a genetic screen was employed to identify mutants defective in NO accumulation after treatment with the physiological inducer hydrogen peroxide. In wild-type Arabidopsis thaliana plants, NO levels increase eightfold in roots after H2O2 treatment for 30 min. A mutant defective in H2O2-induced NO accumulation was identified, and the corresponding mutation was mapped to the prohibitin gene PHB3, converting the highly conserved Gly-37 to an Asp in the protein's SPFH domain. This point mutant and a T-DNA insertion mutant were examined for other NO-related phenotypes. Both mutants were defective in abscisic acid–induced NO accumulation and stomatal closure and in auxin-induced lateral root formation. Both mutants were less sensitive to salt stress, showing no increase in NO accumulation and less inhibition of primary root growth in response to NaCl treatment. In addition, light-induced NO accumulation was dramatically reduced in cotyledons. We found no evidence for impaired H2O2 metabolism or signaling in the mutants as H2O2 levels and H2O2-induced gene expression were unaffected by the mutations. These findings identify a component of the NO homeostasis system in plants and expand the function of prohibitin genes to include regulation of NO accumulation and NO-mediated responses.
Role of the bedrock topography in the Quaternary filling of a giant estuarine basin: the Lower St. Lawrence Estuary, Eastern Canada
Authors: Duchesne Mathieu J. , Pinet Nicolas , Bédard Karine , St‐Onge Guillaume , Lajeunesse Patrick , Campbell D. Calvin , Bolduc Andrée
Published: January 2010

The geometry of estuarine and/or incised‐valley basins and their protected character compared with open sea basins are favourable for the preservation of sedimentary successions. The Lower St. Lawrence Estuary Basin (LSLEB, eastern Canada) is characterized by a thick (>400 m in certain areas) Quaternary succession. High‐ and very high‐resolution seismic reflection data, multibeam bathymetry coverage completed by core and chronostratigraphic data as well as a 3‐D seismic stratigraphic model are used to document the geometrical relationships between the bedrock and the Quaternary units of the LSLEB. The bedrock geometry of LSLEB is characterized by two large troughs that are interpreted as resulting mainly from repeated (?) periods of glacial overdeepening of a pre‐Quaternary drainage system. However, other mechanisms with complex feedback effects such as differential glacio‐isostatic uplift, erosion, sedimentary supply, and subsidence may have contributed to the formation of bedrock troughs. The two large bedrock troughs are mostly filled by ∼200 m thick Wisconsinan (Marine Isotopic Stages 2–4) and possibly older sediments. Overlying units recorded the retreat of the Laurentian Ice Sheet during the Late Wisconsinan (Marine Isotopic Stage 2) and estuarine conditions during the Holocene. The strong correlation existing between the bedrock topography and the thickness of the Quaternary succession is indicative of the effectiveness of the LSLEB as a sediment trap.
Health status of caregivers of children with cerebral palsy
Authors: Byrne M. B. , Hurley D. A. , Daly L. , Cunningham C. G.
Published: January 2010

Background and Aims  While a ‘Family‐Centered’ approach to care is accepted as best practice in the context of childhood disability, it may lead to increased demands on family members by requiring them to be active participants in their child's care. This may impact upon the physical and mental health of the caregiver and therefore needs to be investigated. This study aimed to assess the health status of caregivers of children with cerebral palsy (CP) in Ireland and to identify vulnerable subgroups.

Methods  A cross‐sectional postal survey was conducted using a questionnaire incorporating the SF‐36v2.0. The sample consisted of male and female caregivers of children with CP, representing all levels of ability. Two questionnaires were sent to each child's home; a total of 312 questionnaires were sent to the homes of 156 children.

Results  Completed questionnaires were returned by 161 caregivers (100 women, 61 men) of 101 children, giving a response rate of 65%. Caregivers of children with CP were found to have poorer health than the Irish general population, for whom normative data exist. Female caregivers had poorer health than male caregivers in both the physical (P < 0.05) and mental health (P < 0.001) domains of the SF‐36. Caregivers spending more time caring had significantly poorer mental health than those spending less time caring (P < 0.05). There was no difference in the health of caregivers of ‘more independent’ versus ‘more dependent’ children, apart from the latter group reporting higher levels of bodily pain (P < 0.05).

Conclusion  This study provides evidence of the inferior health status of caregivers of children with CP in Ireland, particularly that of women.
Forty‐four juvenile thieves revisited: from bowlby to reactive attachment disorder
Authors: Follan M. , Minnis H.
Published: January 2010

Background  John Bowlby's work on attachment has had a major influence on practice in child and adolescent psychiatry and developed from observations Bowlby made in his clinical work. In a published case series of work with juvenile offenders, he provided a case description of the differing sets of problems that drove his interest. Clinical features described in a subgroup of these offenders, the ‘affectionless psychopaths’, might be recognized now as reactive attachment disorder (RAD).

Methods  We scrutinized Bowlby's case series ‘44 Juvenile Thieves’ and compared the aetiology and clinical features of a subgroup of these children with the other 74 cases described by Bowlby. We selected one typical case as an exemplar and provide an edited version here. We then present one composite case from a recent study of RAD and provide a comparison with typically developing children.

Results  Of the Bowlby cases, 86% had experienced early prolonged separation from their primary caregivers and had experienced multiple care placements. In total, 10% of clinical comparisons had been similarly separated. In our recent sample, 66% of children experienced separation from primary caregivers compared with none of the comparison group. A similar proportion of our sample of children with RAD had been removed from home as a result of neglect or had experienced other forms of maltreatment.

Conclusions  Bowlby beleived that a main aetiological factor in the development of difficulties was the experience of separation. We suspect that a main aetiological factor in both his and our cases is the experience of maltreatment. We suggest that RAD arises from a complex interplay of genetic and environmental triggers.
Gene expression microarray analysis of heat stress in the soil invertebrate Folsomia candida
Authors: Nota B. , Van Straalen N. M. , Ylstra B. , Roelofs D.
Published: January 2010

Sudden temperature changes in soil can induce stress in soil‐dwelling invertebrates. Hyperthermic conditions have an impact on gene expression as one of the first steps. We use a transcriptomics approach using microarrays to identify expression changes in response to heat in the springtail Folsomia candida. An elevation of temperature (Δ 10 °C) altered the expression of 142 genes (116 up‐, 26 down‐regulated). Many up‐regulated genes encoded heat shock proteins, enzymes involved in ATP synthesis, oxidative stress responsive enzymes and anion‐transporting ATPases. Down‐regulated were glycoside hydrolases, involved in catalysis of disaccharides. The small number of altered transcripts suggest a mild response to heat in this soil invertebrate, but further research is needed to confirm this. This study presents candidate genes for future functional studies concerning thermal stress in soil‐dwelling invertebrates.
Caveat reporting in ultrasound interpretation of surgical pathology: a comparison of sonographer versus radiologist
Authors: Garcea Giuseppe , Mahmoud Asif , Ong Seok Ling , Rees Yvonee , Berry David P. , Dennison Ashely R.
Published: January 2010

Background  Radiology reports provide specialist interpretation of images and relate these findings to the patient's symptoms and signs. This study compared ultrasound (USS) reports generated by radiologists and sonographers to determine if any significant or clinically relevant differences existed.

Methods  A retrospective analysis of 624 consecutive USS reports was carried out. The reports were assessed for the presence of a ‘disclaimer’ or ‘caveat’ pertaining to the quality of the images and were analysed with respect to the clarity of their wording and ability to answer the clinical request.

Results  The majority of sonographer USS reports contained a disclaimer regarding the quality of the USS images (57.1%) compared with a smaller proportion of radiologist scans (9.9%) (P < 0.001). Overall, radiologists performed significantly better in providing a clear negative or positive diagnosis to the clinical question on the request form, when compared with sonographers (88.5% vs. 65.4%, P < 0.001).

Conclusion  ‘Disclaimer’ comments and ‘hedging’ must be avoided in radiology reporting. While feedback as to the accuracy of the radiology images is important, overuse of such terms undermines the validity of the radiology report.
Microstructure evolution in hot worked steel after heating to semi‐solid state
Authors: SOŁEK K. , MITURA Z. , KARBOWNICZEK M. , DUTKIEWICZ J. , FARYNA M. , ROGAL Ł.
Published: January 2010

Metal alloys can be formed successfully in a partially liquid state if they display a particular globular microstructure. The article presents an analysis of a study carried out of the development, by means of the strain‐induced melt‐activated method, of such a microstructure for an X210CrW12 steel. Hot rolled samples, with subsequent cooling, were heated to the temperature range at which the liquid and solid phases coexist in the material. The spheroidal shapes for solid particles, required for semi‐solid processing, were found. The investigations were carried out using scanning electron microscopy in combination with energy dispersive spectroscopy.
TEM and HRTEM studies of ball milled 6061 aluminium alloy powder with Zr addition
Authors: LITYŃSKA‐DOBRZYŃSKA L. , DUTKIEWICZ J. , MAZIARZ W. , ROGAL Ł.
Published: January 2010

The effect of mechanical alloying on the microstructure of atomized 6061 aluminium alloy powder and 6061 powder with a zirconium addition was studied in the work. The atomized 6061 aluminium alloy powder and 6061 powder with addition of 2 wt.% Zr were milled in a planetary ball mill and investigated using X‐ray diffraction measurements, conventional and high‐resolution electron microscopy (TEM/HRTEM) and high‐angle annular dark field scanning transmission electron microscopy combined with energy dispersive X‐ray microanalysis. An increase of stresses was observed in milled powders after the refinement of crystallites beyond 100 nm. In the powder with zirconium addition, some part of the Zr atoms diffused in aluminium forming a solid solution containing up to 0.5 wt.% Zr. The remaining was found to form Zr‐rich particles containing up to 88 wt.% Zr and were identified as face centred cubic (fcc) phase with lattice constant a= 0.48 nm. That fcc phase partially transformed into the L12 ordered phase. Eighty‐hour milling brought an increase of microhardness (measured with Vickers method) from about 50 HV (168 MPa) for the initial 6061 powder to about 170 HV (552 MPa). The addition of zirconium had no influence on the microhardness.
Nuclear‐encoded DnaJ homologue of Plasmodium falciparum interacts with replication ori of the apicoplast genome
Authors: Kumar Ambrish , Tanveer Aiman , Biswas Subir , Ram Edupuganti V. S. Raghu , Gupta Ankit , Kumar Bijay , Habib Saman
Published: January 2010

The apicoplast of Plasmodium falciparum carries a 35 kb circular genome (plDNA) that replicates at the late trophozoite stage of the parasite intraerythocytic cycle. plDNA replication proceeds predominantly via a d‐loop/bi‐directional ori mechanism with replication ori localized within inverted repeat region. Although replication of the apicoplast genome is a validated drug target, the proteins involved in the replication process are only partially characterized. We analysed DNA–protein interactions at a plDNA replication ori region and report the identification of a nuclear‐encoded DnaJ homologue that binds directly to ori elements of the plDNA molecule. PfDnaJA interacted with the minor groove of the DNA double‐helix and recognized a 13 bp sequence within the ori. Inhibition of binding with anti‐PfDnaJA antibodies confirmed identity of the protein in DNA‐binding experiments with organellar protein fractions. The DNA‐binding domain of the ∼69 kDa PfDnaJA lay within the N‐terminal 38 kDa region that carries DnaJ signature motifs. In contrast to PfDnaJA in parasite organellar fractions, the recombinant protein interacted with DNA in a sequence non‐specific manner. Our results suggest a role for PfDnaJA in replication/repair of the apicoplast genome.
PRECLINICAL STUDY: Atypical development of behavioural sensitization to 3,4‐methylenedioxymethamphetamine (MDMA, ‘Ecstasy’) in adolescent rats and its expression in adulthood: role of the MDMA chirality
Authors: Von Ameln Nora , Von Ameln‐Mayerhofer Andreas
Published: January 2010

Despite the great popularity of 3,4‐methylenedioxymethamphetamine (MDMA, Ecstasy) as a drug of abuse, not much is known about the detailed mechanisms of the acute and subchronic effects of the drug. There is especially a lack of information about the distinct behavioural effects of its optical isomers (enantiomers) R‐ and S‐MDMA compared with the racemic RS‐MDMA. For this purpose, adolescent rats were repetitively treated during two treatment stages (stage 1: days 1–10; stage 2: days 15, 17, 19) with RS‐MDMA (5 or 10 mg/kg) or each of the respective enantiomers (5 mg/kg). The repeated treatment started on postnatal day (PND) 32 and locomotor activity was measured on each day by means of a photobeam‐equipped activity box system. RS‐MDMA or S‐MDMA administration led acutely to massive hyperlocomotion and subchronically, to the development of behavioural sensitization after a short habituation period. R‐MDMA was free of hyperactivating effects and even decreased locomotor behaviour upon repeated treatment. Nevertheless, co‐administration of R‐MDMA increased the hyperactivity of S‐MDMA and made the S‐MDMA induced behavioural sensitization state‐dependent. The animals pre‐treated with R‐MDMA showed a sensitized response in adulthood when tested with RS‐MDMA. Our results indicated that even in the absence of substantial neurotoxicity, both MDMA enantiomers can lead to long‐term changes in brain circuitry and concomitant behavioural changes when repeatedly administered in adolescence. The sensitization development was most pronounced in the animals treated with S‐ and RS‐MDMA; the animals with R‐MDMA did not develop sensitization under repeated treatment but expressed a sensitized response when challenged with RS‐MDMA.
Selection for individual recognition and the evolution of polymorphic identity signals in Polistes paper wasps
Authors: Sheehan M. J. , Tibbetts E. A.
Published: January 2010

Individual recognition (IR) requires individuals to uniquely identify their social partners based on phenotypic variation. Because IR is so specific, distinctive phenotypes that stand out from the crowd facilitate efficient recognition. Over time, the benefits of unique appearances are predicted to produce a correlation between IR and phenotypic variation. Here, we test whether there is an association between elevated phenotypic polymorphism and IR in paper wasps. Previous work has shown that Polistes fuscatus use variable colour patterns for IR. We test whether two less variable wasp species, Polistes dominulus and Polistes metricus, are capable of IR. As predicted, neither species is capable of IR, suggesting that highly variable colour patterns are confined to Polistes species with IR. This association suggests that elevated phenotypic variation in taxa with IR may be the result of selection for identity signals rather than neutral processes. Given that IR is widespread among social taxa, selection for identity signalling may be an underappreciated mechanism for the origin and maintenance of polymorphism.