bluuebunny/crossref_metadata_2025 huggingface dataset:
How to go extinct by mating too much: population consequences of male mate choice and efficiency in a sexual–asexual species complex
Authors: Heubel Katja U. , Rankin Daniel J. , Kokko Hanna
Published: January 2009

Selection acting on individuals is not predicted to maximize population persistence, yet examples that explicitly quantify conflicts between individual and population level benefits are scarce. One such conflict occurs over sexual reproduction because of the cost of sex: sexual populations that suffer the cost of producing males have only half the growth rate compared to asexuals. Male behaviour can additionally impact population dynamics in a variety of ways, and here we study an example where the impact is unusually clear: the riddle of persistence of sperm‐dependent sexual–asexual species complexes. Here, a sexually reproducing host species coexists with an ameiotically reproducing all‐female sperm parasite. Sexual–asexual coexistence should not be stable because the proportion of asexually reproducing females will rapidly increase and the relative abundance of the sexually reproducing host species will decline. A severe shortage of males will lead to sperm limitation for sexual and asexual females and the system collapses. Male mate choice could reduce the reproductive potential of the asexual species and thus potentially prevent the collapse. In the gynogenetic (sperm‐dependent parthenogenetic) Amazon molly Poecilia formosa and its host (P. latipinna or P. mexicana), males discriminate against asexual females to some extent. Using a population‐dynamical model, we examine the population dynamics of this species complex with varying strengths of male discrimination ability and efficiency with which they locate females and produce sperm. The sexual species would benefit from stronger discrimination, thus preventing being displaced by the asexual females. However, males would be required to evolve preferences that are probably too strong to be purely based upon selection acting on individuals. We conclude that male behaviour does not fully prevent but delays extinction, yet this is highly relevant because low local extinction rates strongly promote coexistence as a metapopulation.
Impact of dispersal on population growth: the role of inter‐patch distance
Authors: Bowler Diana E. , Benton Tim G.
Published: January 2009

Dispersal can play a key role in the dynamics of patchy populations through patch colonization, and generally this leads to distance‐dependent colonization. Less recognised are the roles of dispersal and inter‐patch distance on the growth of a population after colonization. We use a laboratory mite model system in which both juveniles and adults can disperse to explore the impact of dispersal, and particularly inter‐patch distance, on population dynamics. We examine the dynamics of patches after colonization by manipulating the presence of a dispersal corridor to a source patch at two inter‐patch distances. Consistent with many field studies, the results show colonization was slower in more distant patches. Following colonization, the effect of the dispersal corridor on dynamics was dependent on inter‐patch distance. In patches near the source, the number of adults tended to increase at a faster rate, and juveniles at a slower rate when connected with a dispersal corridor. In contrast, adult numbers grew slower and juveniles tended to grow faster when connected with a corridor in more distant patches. In the long‐term, equilibrium adult numbers were lower in patches connected to the source patch at both distances. These results are likely to be driven by the effects of inter‐patch distance on dispersal mortality, and the effects of dispersal on patch abundance and within‐patch competition. These results confirm that distance is important for patch colonization and also show that distance can affect population density after colonization. The effects of dispersal and distance on local dynamics could be important in the dynamics of patchy populations in increasingly fragmented landscapes.
Species identity, diversity and microbial carbon flow in reassembling macrobenthic communities
Authors: Rossi Francesca , Vos Matthijs , Middelburg Jack J.
Published: January 2009

Intense disturbance may locally destroy patches of habitat and shape the landscape into a mosaic of reassembling communities. The development of ecosystem properties during such community reassembly is poorly understood. In intertidal bare sediments, trophic relations between microphytobenthos or heterotrophic bacteria and macrofauna invertebrates may guarantee fundamental ecosystem properties such as carbon flow through the food web. We studied the dynamic relation between reassembling macrofauna communities and such microbial carbon flow during recovery after severe disturbance. We deliberately induced prolonged hypoxia in winter and early summer and allowed recolonisation for periods of two and five months. Carbon flow was quantified from basal resources (microphytobenthos and bacteria) to intermediate consumers using13C as a tracer. Within the period of study (5 months), microbial carbon flow fully recovered, although macrofauna diversity was still very low compared to the natural communities (ranging from 6 to 17 species). More than 90% of microbial carbon flow to macrofauna was due to the consumers that recolonised within two months. Two of these species were dominant contributors to microphytobenthos carbon transfer to fauna. Furthermore, at an early stage of reassembly, this ecosystem property was remarkably similar when disturbance took place at different times of the year (winter or early summer), although there were differences in assemblage composition and functional diversity. We conclude that species assemblages and ecosystem function developed relatively independently in this benthic system. We discuss which ecological factors may have caused such non‐parallel development of macrofaunal communities and carbon flow.
Poor phenotypic integration of blue mussel inducible defenses in environments with multiple predators
Authors: Freeman Aaren S. , Meszaros John , Byers James E.
Published: January 2009

Aquatic prey encounter an array of threat cues from multiple predators and killed conspecifics, yet the vast majority of induced defenses are investigated using cues from single predator species. In most cases, it is unclear if odors from multiple predators will disrupt defenses observed in single‐predator induction experiments. We experimentally compared the inducible defenses of the common marine mussel Mytilus edulis to waterborne odor from pairwise combinations of three predators representing two attack strategies. Predators included the sea star, Asterias vulgaris (=Asteriasrubens), and the crabs Carcinus maenas and Cancer irroratus. The mussels increased adductor muscle mass in response to cues from unfed Asterias (a predatory seastar that pulls mussel shells open) and increased shell thickness in response to unfed Carcinus, a predatory crab that crushes or peels shells. However, the mussels did not express either predator specific response when exposed to the combined cues of Asterias and Carcinus, and mussels did not increase shell thickness when exposed to cues from Cancer alone or any pairwise combination of the three predators. Shell closure or ‘clamming up’ did not occur in response to any predator combination. These results suggest that predator‐specific responses to the Asterias and Carcinus are poorly integrated and cannot be expressed simultaneously. Simultaneous cues from multiple predators affect the integration of predator specific defenses and predator odors from functionally similar predators do not necessarily initiate similar defenses. Ultimately, the degree that prey can integrate potentially disparate defenses in a multiple predator environment may have ecological ramifications and represent a seldom explored facet of the evolution of inducible defenses.
Effects of body size, trophic mode and larval habitat on Diptera stoichiometry: a regional comparison
Authors: Hambäck Peter A. , Gilbert James , Schneider Katie , Martinson Holly M. , Kolb Gundula , Fagan William F.
Published: January 2009

Ecological stoichiometry has emerged as a tool for exploring nutrient demand and evolutionary responses to nutrient limitation. Previous studies of insects have found predictable variability in stoichiometry, both in relation to body size and trophic mode, at ordinal levels or higher. Our study further examines the evolutionary and ecological lability in these traits by comparing the effects of body size, trophic mode (larval and adult) and larval habitat on the stoichiometry of insects within one order (Diptera). The study also expands on previous work by analyzing trophic mode both at coarse (detritivore, herbivore, predator) and fine (high‐ vs low‐ nutrient quality resources within trophic categories) scales and by comparing nutrient stoichiometry in two geographical regions, Sweden and Arizona. As predicted, adults feeding on nectar or pollen had the lowest body N content in the dataset. Additionally, for Diptera with predatory larvae, species low N diets had lower body N content than those with high N diets. However, body N content was not consistently lower for all species with low N resources, as species feeding on plant material were indistinguishable in stoichiometry from predators with high N diets. We suggest that these results emerge because larval resource exploitation is poorly understood in herbivorous Diptera species. Body P content for Swedish Diptera decreased with body size for all trophic modes, and the only difference among trophic modes was that blood feeders had higher P content than other groups. The regional comparison further showed that the allometry of body P content is a labile trait that may vary at regional scales, as there was no allometric scaling of body P content in the Arizona data set, in contrast to the Swedish data set. These results are not easily explained by existing theoretical frameworks, but instead point to a general context‐dependence of P stoichiometry, which should now be a focus for future work.
Immune responses of bumblebee workers as a function of individual and colony age: senescence versus plastic adjustment of the immune function
Authors: Moret Yannick , Schmid‐Hempel Paul
Published: January 2009

Senescence may evolve in response to externally imposed schedules of survival and reproduction. It may result from cumulative damage to several tissues and organs leading to the progressive malfunction of somatic defences including the immune system, which is a relevant and accessible trait to study the evolution and the mechanisms of senescence.

In social insects, reproduction of workers is negligible and their fitness relies on the colony reproductive success, which depends on workers’ longevity. Consequently, evolution of senescence in workers will rely on age‐dependent survival rate and the residual reproductive value of the colony. Using the bumblebee, Bombus terrestris, as model system, we investigated changes in constitutive and inducible immune defences. Such changes were monitored in relation to worker age and colony age and as well under a high, persistent level of parasitism. The results show that the inducible production of antibacterial peptides was not affected by the age of individual worker or the age of their colony. In contrast, constitutive defences such as haemocyte density and phenoloxidase (PO) activity decline with individual worker age and potential accumulation of physiological defects due to high and persistent levels of parasitism did not explain this pattern of immunosenescence. Interestingly, levels of worker constitutive defences were found to increase with colony age. We found antibacterial activity was strongly traded‐off against PO activity. Such a relationship was not caused by resource shortage. Overall, these data suggest that patterns of variation of immune defences with worker age and colony age are likely the result of plastic temporal adjustments of immune responses in accordance with life history predictions. Hence, control of pathogenic threat in a social system may involve optimal adjustments of immune defences at both the individual and colony levels.
Dominant species can produce a negative relationship between species diversity and ecosystem function
Authors: Creed Robert P. , Cherry Robert P. , Pflaum James R. , Wood Chris J.
Published: January 2009

Several studies have reported a positive relationship between species richness and ecosystem functioning. However, if much of a particular ecosystem function is performed by one species (i.e. a functionally dominant species) and this species is also a competitive dominant that excludes other taxa from a habitat, then it is possible to obtain a negative relationship between richness and ecosystem functioning. Results of a leaf pack breakdown experiment in a small stream suggested that the caddisfly Pycnopsyche gentilis, a common detritivorous insect in North American headwater streams, was both a functional and competitive dominant. In a second experiment we compared the effect of Pycnopsyche on leaf breakdown to that of other detritivore taxa by enclosing them with leaf packs in a section of headwater stream in which they were uncommon (Pycnopsyche transplant experiment). Final leaf pack mass was significantly lower in the Pycnopsyche enclosure treatment; leaves exposed to a greater diversity of detritivores displayed little reduction in leaf mass. These results demonstrated that Pycnopsyche was a functionally dominant detritivore. In a third experiment (Pycnopsyche density experiment) we found that Pycnopsyche was also a competitively dominant species. Leaf packs and large Pycnopsyche were placed in enclosures that were permeable to the majority of other detritivores but not Pycnopsyche. Leaf mass lost increased with increasing Pycnopsyche density. Leaf packs exposed to Pycnopsyche, however, contained fewer detritivore taxa which suggested that Pycnopsyche was also a competitive dominant. There was a negative relationship between three measures of diversity and leaf litter breakdown in the Pycnopsyche density experiment. Experiments conducted in natural communities that incorporate important species interactions may produce diversity‐ecosystem function relationships other than the positive ones that are commonly reported.
Are population differences in plant quality reflected in the preference and performance of two endoparasitoid wasps?
Authors: Gols Rieta , Van Dam Nicole M. , Raaijmakers Ciska E. , Dicke Marcel , Harvey Jeffrey A.
Published: January 2009

In recent years, increasing attention has been paid in exploring the role of direct plant defence, through the production of allelochemicals, on the performance of parasitoid wasps and their hosts. However, few studies have determined if parasitoids can detect differences in plant quality and thus preferentially attack hosts on which their progeny develop most successfully. In this study we examined the development and preference of two endoparasitoids, Diadegmasemiclausum and Cotesia glomerata, developing in larvae of their respective hosts, Plutella xylostella and Pieris brassicae. In turn, these were reared on different wild populations of black mustard Brassica nigra originating in the Netherlands and Sicily (Italy), as well as single cultivated strains of B. nigra and brown mustard, B. juncea. Chemical analyses of foliar glucosinolates and volatile emissions by P. xylostella‐damaged plants revealed large differences between B. nigra and B. juncea plants, with smaller differences among the B. nigra populations. The four mustard populations differentially affected development time and body mass of the herbivores and parasitoids. Contrasts among the means revealed significant differences mainly between B. nigra and B. juncea. Both parasitoids, however, preferred to alight on plants in which their progeny developed most successfully. In behavioural bioassays, D. semiclausum did not discriminate among the B. nigra populations and preferred to alight on B. juncea, which was the best plant population for parasitoid development. By contrast, C. glomerata females exhibited the lowest preference for Italian B. nigra populations, on which adult parasitoid size was the smallest. These results reveal that parasitoids can detect even small differences in plant quality presumably through their volatile blends and that plant preference and offspring performance in the two species are ‘optimally synchronized’.
Geographic variation in body size, sexual size dimorphism and fitness components of a seed beetle: local adaptation versus phenotypic plasticity
Authors: Craig Stillwell R. , Fox Charles W.
Published: January 2009

Variation in body size, growth and life history traits of ectotherms along latitudinal and altitudinal clines is generally assumed to represent adaptation to local environmental conditions, especially adaptation to temperature. However, the degree to which variation along these clines is due to adaptation vs plasticity remains poorly understood. In addition, geographic patterns often differ between females and males – e.g. sexual dimorphism varies along latitudinal clines, but the extent to which these sex differences are due to genetic differences between sexes vs sex differences in plasticity is poorly understood. We use common garden experiments (beetles reared at 24, 30 and 36°C) to quantify the relative contribution of genetically‐based differentiation among populations vs phenotypic plasticity to variation in body size and other traits among six populations of the seed‐feeding beetle Stator limbatus collected from various altitudes in Arizona, USA. We found that temperature induces substantial plasticity in survivorship, body size and female lifetime fecundity, indicating that developmental temperature significantly affects growth and life history traits of S. limbatus. We also detected genetic differences among populations for body size and fecundity, and genetic differences among populations in thermal reaction norms, but the altitude of origin (and hence mean temperature) does not appear to explain these genetic differences. This and other recent studies suggest that temperature is not the major environmental factor that generates geographic variation in traits of this species. In addition, though there was no overall difference in plasticity of body size between males and females (when averaged across populations), we did find that the degree to which dimorphism changed with temperature varied among populations. Consequently, future studies should be extremely cautious when using only a few study populations to examine environmental effects on sexual dimorphism.
Comparison of tissue viability imaging and colorimetry: skin blanching
Authors: Zhai Hongbo , Chan Heidi P. , Farahmand Sara , Nilsson Gert E. , Maibach Howard I.
Published: January 2009

Background: Operator‐independent assessment of skin blanching is important in the development and evaluation of topically applied steroids. Spectroscopic instruments based on hand‐held probes, however, include elements of operator dependence such as difference in applied pressure and probe misalignment, while laser Doppler‐based methods are better suited for demonstration of skin vasodilatation than for vasoconstriction.

Objective: To demonstrate the potential of the emerging technology of Tissue Viability Imaging (TiVi) in the objective and operator‐independent assessment of skin blanching.

Methods: The WheelsBridge TiVi600 Tissue Viability Imager was used for quantification of human skin blanching with the Minolta chromameter CR 200 as an independent colorimeter reference method. Desoximetasone gel 0.05% was applied topically on the volar side of the forearm under occlusion for 6 h in four healthy adults. In a separate study, the induction of blanching in the occlusion phase was mapped using a transparent occlusion cover.

Results: The relative uncertainty in the blanching estimate produced by the Tissue Viability Imager was about 5% and similar to that of the chromameter operated by a single user and taking the a* parameter as a measure of blanching. Estimation of skin blanching could also be performed in the presence of a transient paradoxical erythema, using the integrated TiVi software. The successive induction of skin blanching during the occlusion phase could readily be mapped by the Tissue Viability Imager.

Conclusion: TiVi seems to be suitable for operator‐independent and remote mapping of human skin blanching, eliminating the main disadvantages of methods based on hand‐held probes.
The interdental gingiva, a visible guide for placement of mini‐implants
Authors: Chun YS , Lee SK , Wikesjö UME , Lim WH
Published: January 2009

Structured Abstract

Authors –  Chun YS, Lee SK, Wikesjö UME, Lim WH

Objectives –  To determine whether the tip of the interdental gingiva can serve as a visible guide for placement of mini‐implants.

Setting and Sample population –  Computer tomography (CT) images from 15 males and 15 females (mean age 27 years, range: 23–35 years) were used to evaluate the distance from the tip of the interdental gingiva to the alveolar crest from the central incisor to the 1st molar. The distance from a reference point to the tip of interdental gingiva was recorded from study models using a caliper. The distance between the reference point and the alveolar crest was recorded using CT and added to the model recordings thus providing the distance from the tip of interdental gingiva to the alveolar crest for the various interdental sites. Two‐way anova and Student–Newman–Keuls test for multiple comparisons were used for the statistical analysis.

Results –  There was no significant difference in the distance from the tip of interdental gingiva to the alveolar crest between maxilla and mandible. The distance between the tip of interdental gingiva and the alveolar crest at the central/lateral incisors was the shortest compared with that of other sites. There was also a statistically significant difference between the male and female groups except for the maxillary 2nd premolar/1st molar interradicular site.

Conclusion –  The tip of interdental gingiva appears a reasonable visual guide for the placement of mini‐implants for orthodontic anchorage.
Ichthyoses – Part 1: Differential diagnosis of vulgar ichthyoses and therapeutic options
Authors: Krug Markus , Oji Vinzenz , Traupe Heiko , Berneburg Mark
Published: January 2009

Ichthyoses are a group of genetic disorders with defective cornification, clinically characterized by scaling of the skin. Additionally, distinctive cutaneous inflammation can often be observed. For most of the patients these diseases lead to a significant restriction in quality of life. The diagnostic criteria include clinical and histological findings, often confirmed by specialized tests. Because many of the ichthyoses are extremely rare, their accurate diagnosis is often carried out in specialized centers. We summarize isolated vulgar and congenital ichthyoses both with and without associated symptoms and focus on the common genetic changes and their clinical phenotype. Specific therapies are still not available for most of these genetic disorders. The use of different topical agents (e. g. urea, retinoids and salicylic acid) and baths followed by mechanical keratolysis (sometimes in combination with systemic retinoids) reduce symptoms. Patients with uncommon congenital ichthyoses often benefit from interdisciplinary management which involves specialized dermatological centers.

In this first part of the paper the vulgar ichthyoses as well as the diagnostic and therapeutic options are discussed. The second part focuses on the congenital ichthyoses and their differential diagnosis.
Ichthyoses – Part 2: Congenital ichthyoses
Authors: Krug Markus , Oji Vinzenz , Traupe Heiko , Berneburg Mark
Published: January 2009

Congenital ichthyoses are a group of genetic disorders with defective cornification, clinically characterized by scaling of the skin. Additionally, distinctive cutaneous inflammation can often be observed. For most of the patients these diseases lead to a significant restriction in quality of life. The diagnostic hallmarks are discussed. The diagnostic criteria include clinical and histological findings, often enhanced or confirmed by specialized tests. Because many of the congenital ichthyoses are extremely rare, their accurate diagnosis is often carried out in specialized centers. After discussing the vulgar ichthyoses as well as the diagnostic and therapeutic options in part one, in this second part we review congenital ichthyoses both with and without associated symptoms, focusing on the common genetic changes and their clinical phenotype. Specific therapies are still not available for most of these disorders. The use of different topical agents (e. g. urea, retinoids and salicylic acid) and baths followed by mechanical keratolysis (sometimes in combination with systemic retinoids) reduce skin symptoms. Patients with uncommon congenital ichthyoses often benefit from interdisciplinary management which involves specialized dermatological centers.
The diagnostic protocol in children and adolescents with syncope: a multi‐centre prospective study
Authors: Zhang Qingyou , Du Junbao , Wang Cheng , Du Zhongdong , Wang Li , Tang Chaoshu
Published: January 2009

Aim: The appropriate diagnostic protocol for children with syncope has not been well established. A diagnostic protocol was developed and prospectively implemented to improve the diagnostic performance of paediatricians.

Methods: The study population included 474 consecutive patients (range 6–17 years) presenting with a syncopal spell in one of the five participating hospitals of China. In step 1, all patients underwent initial evaluation for history, physical examination, standing test and standard electrocardiography (ECG). In step 2, priority was given to cardiographic tests for possibly cardiogenic syncope, or electroencephalographic examination and brain imaging for suspected neurological syncope, or psychiatric tests for suspected psychiatric syncope. Patients with unexplained syncope underwent head‐up tilt testing (HUT).

Results: The initial evaluation gave a definite diagnosis in 59 (12.4%) and possible diagnosis in 54 of the 474 patients. Further testing gave a definite diagnosis for 326 patients (69.7%). After the entire diagnostic protocol, definite diagnosis was established in 385 patients (81.1%). Autonomic‐mediated reflex syncope (AMS) accounted for 73.0% of cases. The average cost of diagnostic results per patient was RMB 1030.24 ± 150.09 ($118.42 ± 17.25).

Conclusion: The use of a simplified diagnostic protocol for children and adolescents with syncope improves diagnostic yield.
Vagal bradycardia at term
Authors: Delcò Cristina , Beghetti Maurice , Pfister Riccardo E
Published: January 2009

We discuss the case of a newborn boy presenting well into term with severe bradycardic events and sinus pauses up to 5.4 sec. Sinus bradycardia below 80 bpm and sinus pauses or asystole of more than 2 sec are considered pathologic at term. After exclusion of specific causes, the diagnosis of vagal hyper‐reflectivity (VHR) was retained, a state caused by unbalance between sympathetic and parasympathetic activity, the latter overriding the former. It is thought to be a functional and transitional anomaly of the sympathetic and vagal tone during the first months of life and may lead to prolonged monitoring and delayed hospital discharge. This form of rare bradycardia can be treated with atropine and allowed in our case immediate resolution of events and safe discharge from hospital.

Conclusion: When VHR is diagnosed, atropine is the treatment permitting resolution of symptomatic episodes of bradycardia and early and safe discharge from hospital.
Corporate fraud and investment distortions in efficient capital markets
Authors: Kumar Praveen , Langberg Nisan
Published: January 2009

Inefficient investment allocation induced by corporate fraud, where informed insiders strategically manipulate outside investors' beliefs, has been endemic historically and has recently attracted much attention. We reconcile corporate fraud and investment distortions with efficient capital markets, building on shareholder‐manager agency conflicts and investment renegotiation in active takeover markets. Because investments that are ex post inefficient are not renegotiation proof, the optimal renegotiation‐proof contract induces overstatements by managers, accompanied by overinvestment in low return states and underinvestment in high return states by rational investors. Our framework also helps explain why easy access to external capital appears to facilitate corporate fraud.
Coordination and delay in hierarchies
Authors: Patacconi Andrea
Published: January 2009

This article studies hierarchical organizations where concerns for fast execution are important and employees must be coordinated to avoid wasteful duplications of effort. Simple conditions are provided for the time spent on coordinating subordinates to be increasing and the span of control to be decreasing as one goes up the hierarchy, with equalities holding if delay is all that matters. When returns to specialization are substantial, the span of control also tends to widen and the hierarchy to flatten as urgency increases. The model suggests that concerns for fast execution may be key in explaining recent trends toward decentralization and delayering in firms.
A Low-Dimensional Sagittal-Plane Forward-Dynamic Model for Asymmetric Gait and Its Application to Study the Gait of Transtibial Prosthesis Users
Authors: Srinivasan S. , Westervelt E. R. , Hansen A. H.
Published: January 2009

This paper presents an extension of a recently developed low-dimensional modeling approach for normal human gait to the modeling of asymmetric gait. The asymmetric model is applied to analyze the gait dynamics of a transtibial prosthesis user, specifically the changes in joint torque and joint power costs that occur with variations in sagittal-plane alignment of the prosthesis, mass distribution of the prosthesis, and roll-over shape of the prosthetic foot being used. The model predicts an increase in cost with addition of mass and a more distal location of the mass, as well as the existence of an alignment at which the costs are minimized. The model’s predictions also suggest guidelines for the selection of prosthetic feet and suitable alignments. The results agree with clinical observations and results of other gait studies reported in the literature. The model can be a useful analytical tool for more informed design and selection of prosthetic components, and provides a basis for making the alignment process systematic.
Development of a Three-Dimensional Bioprinter: Construction of Cell Supporting Structures Using Hydrogel and State-Of-The-Art Inkjet Technology
Authors: Nishiyama Yuichi , Nakamura Makoto , Henmi Chizuka , Yamaguchi Kumiko , Mochizuki Shuichi , Nakagawa Hidemoto , Takiura Koki
Published: January 2009

We have developed a new technology for producing three-dimensional (3D) biological structures composed of living cells and hydrogel in vitro, via the direct and accurate printing of cells with an inkjet printing system. Various hydrogel structures were constructed with our custom-made inkjet printer, which we termed 3D bioprinter. In the present study, we used an alginate hydrogel that was obtained through the reaction of a sodium alginate solution with a calcium chloride solution. For the construction of the gel structure, sodium alginate solution was ejected from the inkjet nozzle (SEA-Jet™, Seiko Epson Corp., Suwa, Japan) and was mixed with a substrate composed of a calcium chloride solution. In our 3D bioprinter, the nozzle head can be moved in three dimensions. Owing to the development of the 3D bioprinter, an innovative fabrication method that enables the gentle and precise fixation of 3D gel structures was established using living cells as a material. To date, several 3D structures that include living cells have been fabricated, including lines, planes, laminated structures, and tubes, and now, experiments to construct various hydrogel structures are being carried out in our laboratory.
Cartilage Collagen Matrix Reorientation and Displacement in Response to Surface Loading
Authors: Moger C. J. , Arkill K. P. , Barrett R. , Bleuet P. , Ellis R. E. , Green E. M. , Winlove C. P.
Published: January 2009

An investigation of collagen fiber reorientation, as well as fluid and matrix movement of equine articular cartilage and subchondral bone under compressive mechanical loads, was undertaken using small angle X-ray scattering measurements and optical microscopy. Small angle X-ray scattering measurements were made on healthy and diseased samples of equine articular cartilage and subchondral bone mounted in a mechanical testing apparatus on station ID18F of ESRF, Grenoble, together with fiber orientation analysis using polarized light and displacement measurements of the cartilage matrix and fluid using tracers. At surface pressures of up to approximately 1.5 MPa, there was reversible compression of the tangential surface fibers and immediately subjacent zone. As load increased, deformation in these zones reached a maximum and then reorientation propagated to the radial deep zone. Between surface pressures of 4.8 MPa and 6.0 MPa, fiber orientation above the tide mark rotated 10 deg from the radial direction, with an overall loss of alignment. With further increase in load, the fibers “crimped” as shown by the appearance of subsidiary peaks approximately ±10 deg either side of the principal fiber orientation direction. Failure at higher loads was characterized by a radial split in the deep cartilage, which propagated along the tide mark while the surface zone remained intact. In lesions, the fiber organization was disrupted and the initial response to load was consistent with early rupture of fibers, but the matrix relaxed to an organization very similar to that of the unloaded tissue. Tracer measurements revealed anisotropic solid and fluid displacement, which depended strongly on depth within the tissue.
PIV-POD Investigation of the Wake of a Sharp-Edged Flat Bluff Body Immersed in a Shallow Channel Flow
Authors: Singha Arindam , Shinneeb A.-M. , Balachandar Ram
Published: January 2009

This paper reports particle-image velocimetry measurements of instantaneous velocity fields in the wake of a sharp-edged bluff body immersed vertically in a shallow smooth open channel flow. The maximum flow velocity was 0.19 m/s and the Reynolds number based on the water depth was 18,270. The purpose of the present study is to show the vertical variation of the velocity field in the near region of a shallow wake. Measurements of the flow field in the vertical central plane and in the horizontal near-bed, mid-depth, and near-surface planes were taken. Then, the mean flow quantities such as the mean velocity, turbulence intensity, and Reynolds stress fields were investigated. In addition, the proper orthogonal decomposition technique was used to reconstruct the velocity fields to investigate the energetic vortical structures. The results showed that the largest recirculation zone in the mean velocity fields occurred in the mid-depth velocity field, while the smallest one occurred near the bed. Also, the fluid was entrained from the sides toward the wake central plane in the three horizontal velocity fields but with different rates. This behavior was attributed to the existence of quasi-streamwise vortices near the boundaries. In addition, patterns of ejection and sweep events near the free surface similar to the features commonly observed near the wall-bounded flows were observed.
Molecular Mechanisms of HipA-Mediated Multidrug Tolerance and Its Neutralization by HipB
Authors: Schumacher Maria A. , Piro Kevin M. , Xu Weijun , Hansen Sonja , Lewis Kim , Brennan Richard G.
Published: January 2009

Bacterial multidrug tolerance is largely responsible for the inability of antibiotics to eradicate infections and is caused by a small population of dormant bacteria called persisters. HipA is a critical
Escherichia coli
persistence factor that is normally neutralized by HipB, a transcription repressor, which also regulates
hipBA
expression. Here, we report multiple structures of HipA and a HipA-HipB-DNA complex. HipA has a eukaryotic serine/threonine kinase–like fold and can phosphorylate the translation factor EF-Tu, suggesting a persistence mechanism via cell stasis. The HipA-HipB-DNA structure reveals the HipB-operator binding mechanism, ∼70° DNA bending, and unexpected HipA-DNA contacts. Dimeric HipB interacts with two HipA molecules to inhibit its kinase activity through sequestration and conformational inactivation. Combined, these studies suggest mechanisms for HipA-mediated persistence and its neutralization by HipB.
Dust Formation in a Galaxy with Primitive Abundances
Authors: Sloan G. C. , Matsuura M. , Zijlstra A. A. , Lagadec E. , Groenewegen M. A. T. , Wood P. R. , Szyszka C. , Bernard-Salas J. , van Loon J. Th.
Published: January 2009

Interstellar dust plays a crucial role in the evolution of galaxies. It governs the chemistry and physics of the interstellar medium. In the local universe, dust forms primarily in the ejecta from stars, but its composition and origin in galaxies at very early times remain controversial. We report observational evidence of dust forming around a carbon star in a nearby galaxy with a low abundance of heavy elements, 25 times lower than the solar abundance. The production of dust by a carbon star in a galaxy with such primitive abundances raises the possibility that carbon stars contributed carbonaceous dust in the early universe.
Broadband Ground-Plane Cloak
Authors: Liu R. , Ji C. , Mock J. J. , Chin J. Y. , Cui T. J. , Smith D. R.
Published: January 2009

The possibility of cloaking an object from detection by electromagnetic waves has recently become a topic of considerable interest. The design of a cloak uses transformation optics, in which a conformal coordinate transformation is applied to Maxwell's equations to obtain a spatially distributed set of constitutive parameters that define the cloak. Here, we present an experimental realization of a cloak design that conceals a perturbation on a flat conducting plane, under which an object can be hidden. To match the complex spatial distribution of the required constitutive parameters, we constructed a metamaterial consisting of thousands of elements, the geometry of each element determined by an automated design process. The ground-plane cloak can be realized with the use of nonresonant metamaterial elements, resulting in a structure having a broad operational bandwidth (covering the range of 13 to 16 gigahertz in our experiment) and exhibiting extremely low loss. Our experimental results indicate that this type of cloak should scale well toward optical wavelengths.
Reflections for Looking Forward
Authors: Hackett Edward J.
Published: January 2009

Insatiable Curiosity
. Innovation in a Fragile Future.
By Helga Nowotny
. Translated from the German () by Mitch Cohen. MIT Press, Cambridge, MA, 2008. 193 pp. $30, £19.95. ISBN 9780262141031.

In this meditation on the future, Nowotny argues that science brings uncertainties and innovation subsequently allows us to cope with them.
Immune Response in Infants to the Heptavalent Pneumococcal Conjugate Vaccine against Vaccine-Related Serotypes 6A and 19A
Authors: Lee Hyunju , Nahm Moon H. , Burton Robert , Kim Kyung-Hyo
Published: January 2009

The currently available 7-valent pneumococcal conjugate vaccine (PCV7) elicits good immune response to and is effective against vaccine serotypes. However, its effectiveness against vaccine-related serotypes is variable. Serum samples were obtained 1 month after the last vaccination from 31 infants immunized with PCV7 at 2, 4, and 6 months of age. The sera were used to determine immunoglobulin G antibody levels to eight serotypes (seven vaccine serotypes and serotype 19A) with enzyme-linked immunosorbent assay (ELISA) and opsonic capacity against 11 serotypes (seven vaccine serotypes, serotypes 19A and 6A, and nonvaccine serotypes 5 and 7F) using a multiplexed opsonization assay. ELISA results showed antibody concentrations varied between 1.84 and 10.49 μg/ml, and all subjects had antibody concentrations of ≥0.35 μg/ml for all serotypes, including serotype 19A. In contrast, the opsonic index was detectable (i.e., opsonic index ≥ 8) in all children for the seven vaccine serotypes, 81% for serotype 6A, and merely 19% for serotype 19A. PCV7 shows good immunogenicity for vaccine serotypes in infants after a primary series. PCV7 does not elicit opsonic antibodies to serotype 19A. ELISA may thus be an inadequate surrogate assay for evaluating the response for cross-reactive serotypes in infants.
Orientia tsutsugamushiBacteremia and Cytokine Levels in Vietnamese Scrub Typhus Patients
Authors: Kramme Stefanie , Van An Le , Khoa Nguyen Dinh , Van Trin Le , Tannich Egbert , Rybniker Jan , Fleischer Bernhard , Drosten Christian , Panning Marcus
Published: January 2009

Scrub typhus, caused by the intracellular bacteriumOrientia tsutsugamushi, is a major cause of febrile illness in the Asia/Pacific region. Here, we implemented a novel real-time PCR and determined the relation of DNA target gene concentration with serum cytokine levels. The limit of detection of the novel real-time PCR was 1,062 DNA copies per ml of EDTA whole blood. Specificity was excellent as determined on a panel of blood- and skin-borne bacteria, includingRickettsiaspp. as well as healthy Vietnamese blood donors. Bacterial DNA concentrations after 9 to 12 days from symptoms onset were significantly higher than in earlier or later periods (P< 0.05). Significantly higher concentrations of gamma interferon (IFN-γ) and interleukin-10 (IL-10) occurred during the acute phase of disease (<10 days from onset) as opposed to the convalescent phase (P< 0.05). No significant differences were observed between the acute and the convalescent phases for tumor necrosis factor alpha (TNF-α) and IL-1β concentrations. Regression analysis of DNA concentrations and cytokine levels identified a significant positive relationship for IL-10 (P< 0.0182) but not for IFN-γ, TNF-α, and IL-1β. In conclusion, proinflammatory cytokines and IL-10 were differentially related to human bacteremia. They may thus be induced by different constituents ofO. tsutsugamushi. As a future prospect in a clinical diagnostic laboratory, quantitative real-time PCR may serve as a reliable tool to monitor therapy and to detect treatment failure.
Detection of VirulentRhodococcus equiin Exhaled Air Samples from Naturally Infected Foals
Authors: Muscatello G. , Gilkerson J. R. , Browning G. F.
Published: January 2009

VirulentRhodococcus equicauses pyogranulomatous bronchopneumonia in foals. The route of infection of foals has been considered to be inhalation of aerosolized bacteria from soil that is contaminated with equine feces. Thus, disease caused byR. equihas been regarded as an opportunistic infection of environmental origin and not a contagious disease. In this study, we report the exhalation of virulentR. equifrom the respiratory tract of naturally infected foals. A handheld air-monitoring system was used to recover virulentR. equifrom the exhaled breath of foals, and the concentration of virulentR. equiorganisms in exhaled air was compared to the concentration in environmental air samples taken from the holding pens and lane areas on farms.R. equistrains carrying thevapAgene of the virulence plasmid were detected by using colony blotting and DNA hybridization techniques in cultures of exhaled air from 67% (37/55) of foals tested. The concentration of virulentR. equiorganisms in exhaled air from foals was significantly higher than that in environmental air (P< 0.001). There were no significant differences in the median concentrations of virulentR. equibacteria exhaled by clinically healthy or diseased foals. The high concentrations of virulentR. equibacteria in exhaled air suggested that aerosol transmission between foals is possible and may have a significant impact on the prevalence ofR. equipneumonia on farms. The air sampling technique described is potentially useful as a noninvasive method for the detection and quantification of virulentR. equiin the respiratory tract of foals.
Simultaneous Detection and Quantitation of Cytomegalovirus, Epstein-Barr Virus, and Adenovirus by Use of Real-Time PCR and Pooled Standards
Authors: Gunson R. N. , Maclean A. R. , Shepherd S. J. , Carman W. F.
Published: January 2009

Quantitative real-time PCR has become the most widely used preemptive approach for managing cytomegalovirus (CMV), Epstein-Barr virus (EBV), and adenovirus infections in immunosuppressed patients. These three assays are normally available as separate tests, each using five quantitation standards that are tested in duplicate. We have developed an adenovirus-CMV-EBV triplex assay that uses one set of five pooled quantitative standards, tested singly rather than in duplicate. This test demonstrated a sensitivity and an accuracy of quantitation equivalent to those of our previous single tests and was shown to be able to detect mixed infections with no loss in sensitivity. This assay is now in routine use in our laboratory and has considerably simplified the work flow of the laboratory, with a resultant improvement in sample turnaround time and significantly reduced costs.
Association of Unique, Isolated Treponemes with Bovine Digital Dermatitis Lesions
Authors: Evans Nicholas J. , Brown Jennifer M. , Demirkan Ibrahim , Singh Prem , Getty Brian , Timofte Dorina , Vink W. Daan , Murray Richard D. , Blowey Roger W. , Birtles Richard J. , Hart C. Anthony , Carter Stuart D.
Published: January 2009

This study used a PCR-based approach targeting 16S rRNA gene fragments to determine the occurrence and association of the three bovine digital dermatitis (BDD) treponeme phylogroups within lesions found in cattle from the United Kingdom. Examination of 51 BDD lesions collected from infected cattle across the United Kingdom revealed that BDD treponeme group 1 (
Treponema medium
/
Treponema vincentii
-like), group 2 (
Treponema phagedenis
-like), and group 3 (
Treponema putidum
/
Treponema denticola
-like) were present in 96.1%, 98%, and 76.5% of BDD lesions, respectively. The three phylogroups were present together in 74.5% of lesions. The PCR assays enabled the isolation of further treponeme strains from previously mixed primary BDD lesion cultures. Here a representative from each of the three distinct treponeme phylogroups was isolated from a single BDD lesion for the first time. These data highlight the extent to which this disease is polytreponemal. Immunohistochemistry and electron microscopy were used to investigate lesional hoof tissues, resulting in treponemes being identified copiously in hair follicles and sebaceous glands, suggesting a potential route of exit and/or entry for these pathogens. This study gives further evidence for the importance of the three treponeme groups in BDD pathogenesis and reiterates the value of molecular genetic approaches for isolating and identifying fastidious anaerobes.
Performance Evaluation of the VersaTREK Blood Culture System for Quality Control Testing of Platelet Units
Authors: Nanua Suparna , Weber Carol , Isgriggs Liz , Dunne W. Michael
Published: January 2009

The performance of the VersaTREK blood culture system for the detection of a bacterial contamination of platelet concentrates was assessed using samples spiked with serial dilutions of nine bacterial species associated with platelet contamination. The system detected growth for all organisms in <20 h, and the detection sensitivity was <20 CFU/ml.
High Concentrations of Manganese in Mueller-Hinton Agar Increase MICs of Tigecycline Determined by Etest
Authors: Fernández-Mazarrasa Carlos , Mazarrasa Olav , Calvo Jorge , del Arco Asunción , Martínez-Martínez Luis
Published: January 2009

MICs of tigecycline determined by Etest were 4 to 12 times (three ATCC strains) and 2 to 8 times (50 clinical isolates) higher in Mueller-Hinton agar from Merck than in Mueller-Hinton agar from either Oxoid or Difco. This was related to a much higher concentration of manganese in the medium from Merck.