bluuebunny/crossref_metadata_2025_split huggingface dataset:
Do standard measures of immunocompetence reflect parasite resistance? The case of Greenfinch coccidiosis
Authors: SAKS L. , KARU U. , OTS I. , HÕRAK P. 
Published: March 2006

SummaryMuch research in evolutionary animal ecology is currently focused on issues related to parasite‐mediated selection. Because of difficulties in estimation of actual parasite resistance, researchers often rely on surrogate measures of immunocompetence, such as the magnitude of immune responses to artificial antigens, assuming that these measures correlate with individuals’ ability to resist disease.This assumption was tested in the Greenfinch (Carduelis chlorisL.) coccidiosis model by measuring the association between parasite resistance and two standard assays of immune function – a swelling response to phytohaemagglutinin (PHA) and antibody production against sheep red blood cells (SRBC).Before performing immune challenge assays, host resistance to the intestinal parasiteIsospora lacazei(Labbe) was assessed on the basis of individual infection intensities and responses to challenge infection with alien parasite strains.Increases in infection intensities after inoculation of birds with novel parasite strains correlated positively with magnitude of swelling response to PHA injection. Thus, intense parasite multiplication in the host's digestive tract resulted in the enhancement of the host's cell‐mediated immune function.Among birds that were vulnerable to novel infections, no correlations emerged between infection intensities, SRBC antibody titres and condition indices.Among non‐vulnerable hosts (whose infection intensities did not increase after experimental reinfection), SRBC antibody titres correlated negatively with infection intensities and positively with indices of nutritional condition. Hence, high SRBC antibody titres reflected good nutritional status and superior resistance to an important parasite species in a subsample of studied Greenfinches.Altogether, our results exemplify the diversity of outcomes when the host's immune system is simultaneously challenged by natural enemies and artificial antigens, and call for the cautious interpretation of the results of standard immune tests in the context of parasite resistance.
Does speed help you survive? A test with Collared Lizards of different ages
Authors: HUSAK J. F. 
Published: March 2006

Summary

While it is generally accepted that the evolution of morphological traits is mediated by selection on whole‐animal performance, few studies have examined how variation in performance explains variation in fitness. Most studies to date have studied how performance predicts survival, and these typically examine only a single age class.
Maximal sprint speed was measured for hatchling and adult Collared Lizards (Crotaphytus collaris), in addition to morphological measurements, in order to determine how well annual survival could be predicted by performance and whether the relationship between performance and survival differed between age classes.
Logistic regression revealed that no morphological trait or sprint speed performance predicted survival in adults. However, sprint speed predicted survival in hatchlings. Further, hindlimb length differed between survivors and non‐survivors and correlated with sprint speed, suggesting that the evolution of hindlimb length in hatchlings may be driven by selection on sprint speed performance.
Selection on sprint speed may be mediated directly by predators where hatchlings cannot attain speeds sufficient to escape predators or indirectly where slower individuals use a greater proportion of their maximal capacity than faster individuals while escaping predators, perhaps causing elevated stress levels or a higher expenditure of energy stores.
Asynchronous hatching in Nicrophorus vespilloides, an insect in which parents provide food for their offspring
Authors: SMISETH P. T. , WARD R. J. S. , MOORE A. J. 
Published: March 2006

Summary

Asynchronous hatching has been studied extensively in altricial birds that feed their offspring, but this phenomenon is also known to occur in insects where parents provide food for their offspring.
We examined the proximate mechanisms underlying asynchronous hatching in the burying beetle Nicrophorus vespilloides, an insect species in which parents feed their offspring.
Mean hatching spread was 30 h. As expected if egg‐laying was the major proximate mechanism underlying variation in hatching patterns, the duration of the egg‐laying period had a highly significant and positive effect on hatching spread. The duration of the egg‐laying period was unrelated to clutch size.
Hatching spread was slightly but significantly reduced compared with the duration of the egg‐laying period, and the last eggs laid by females developed slightly but significantly faster than the first eggs. There was no significant difference in the size of the larvae that hatched from the first and last eggs laid by females.
We discuss the value of N. vespilloides and other insects where parents provide food for their offspring as alternative models to birds for the evolution of asynchronous hatching.
Eye size, foraging methods and the timing of foraging in shorebirds
Authors: THOMAS R. J. , SZÉKELY T. , POWELL R. F. , CUTHILL I. C. 
Published: March 2006

SummaryBirds with large eyes can achieve a greater pupil diameter and/or focal length, and hence, all other things being equal, greater visual sensitivity and resolution than birds with small eyes. Thus eye size is predicted to reflect adaptations to ecology.We tested three predictions about the relationships between eye size, foraging method (from wholly visual to tactile techniques) and the daily pattern of foraging activity (diurnal/nocturnal) in shorebirds, using phylogenetic comparative methods.We found that shorebirds that forage at night were more likely to have large eyes, but species using vision to detect their prey did not have larger eyes than species that detect their prey by touch. We also found no evidence that nocturnal foragers are more likely than diurnal foragers to use tactile rather than visual cues to detect their prey.These results indicate that evolutionary changes toward nocturnal habits are associated with increases in eye size, and thus with increases in aspects of visual capacity, but that foraging mode may not be the prime selective force in this taxon.
Sphagnum modifies climate‐change impacts on subarctic vascular bog plants
Authors: DORREPAAL E. , AERTS R. , CORNELISSEN J. H. C. , VAN LOGTESTIJN R. S. P. , CALLAGHAN T. V. 
Published: March 2006

Summary

Vascular plant growth forms in northern peatlands differ in their strategies to cope with the harsh climate, low nutrient availability and progressively increasing height of the Sphagnum carpet in which they grow. Climate change may therefore affect growth forms differentially, both directly and through changes in the length growth of Sphagnum mosses. However, the role of mosses as modifiers of climate‐change effects on vascular plants has been largely overlooked so far. We investigated the direct and Sphagnum‐mediated effects of experimental changes in summer, winter and spring climate on four species of contrasting growth forms (evergreen and deciduous shrubs, graminoid, forb) in a subarctic bog, by studying their biomass and nitrogen losses through leaf litter, and the length growth of the two shrubs.
Direct and indirect effects of summer warming differed among the growth forms. Enhanced Sphagnum overgrowth of leaves due to summer warming initially stimulated leaf litter losses of the evergreen shrub Empetrum nigrum. However, changes in its shoot morphology, related to an apparent small increase in its length growth, prevented further effects. A stronger increase in stem growth of the deciduous shrub Betula nana in response to summer warming directly reduced its leaf litter mass, N concentration and N losses. The changed allocation prevented indirect, Sphagnum‐mediated effects on its leaf and N dynamics through overgrowth of buds. In contrast, leaf litter mass, N concentrations or N losses of the forb Rubus chamaemorus and the graminoid Calamagrostis lapponica were not affected by summer warming or enhanced Sphagnum growth.
Increases in winter snow cover, with or without spring warming, did not affect shrub growth, nor the total shoot leaf litter mass or N dynamics of any of the growth forms.
Altogether, summer warming is likely to enhance Sphagnum overgrowth of small shrubs with a limited growth response such as Empetrum. Moreover, increased vertical growth may allow Sphagnum to keep pace with inclined growing, responsive shrubs such as Betula. This might prevent net longer‐term positive effects of summer warming on the vascular plant canopy height. However, leaf litter and N losses are more likely to be affected by direct warming effects on shoot morphology and allocation than by Sphagnum growth. The different responses of the growth forms to summer warming suggest that both direct and Sphagnum‐mediated climate effects have the potential to change the vascular plant community and N dynamics in peatlands.
Dietary routing of nutrients from prey to offspring in a generalist predator: effects of prey quality
Authors: RICKERS S. , LANGEL R. , SCHEU S. 
Published: March 2006

Summary

Reproduction of female wolf spiders (Pardosa lugubris; Lycosidae) fed with prey of different quality was investigated. Spiders were fed either a single diet of Drosophila melanogaster (Diptera, high quality), Heteromurus nitidus (Collembola, high quality) or Folsomia candida (Collembola, toxic), or a mixed diet of D. melanogaster and H. nitidus, and of D. melanogaster and F. candida.
Nutrient flow from prey into females and from females into offspring during egg production was investigated tracing carbon and nitrogen stable isotopes with prey being enriched in 13C and/or 15N.
There was no benefit of mixing different high‐quality prey on female biomass and performance, contrasting with earlier results obtained with juvenile spiders.
Folsomia candida was toxic for P. lugubris: females, even if fed a mixed diet also containing high‐quality prey, did not reproduce and finally died; spiders did not acquire aversion against F. candida.
Tracing stable isotopes documented the incorporation of C and N from prey into females and their offspring; dietary nutrients were routed almost exclusively into egg production.
Stable isotope analysis strongly supported the assumption that F. candida causes post‐ingestive physiological effects in spiders by inhibiting the incorporation of nutrients from other prey.
Co‐variations in litter decomposition, leaf traits and plant growth in species from a Mediterranean old‐field succession
Authors: KAZAKOU E. , VILE D. , SHIPLEY B. , GALLET C. , GARNIER E. 
Published: March 2006

Summary

A growing consensus is developing that the impact of species on ecosystem properties is mediated, at least partially, by the traits of their component species. A previous study demonstrated that the field decomposition of complex litters produced by different communities of a Mediterranean successional sere was related to the average trait value of these communities. Here we scale down to the species level, to test whether similar relationships are found for selected species from these communities. We also test whether litter decomposability can be considered as part of the suite of traits characterizing the fast–slow growth continuum in plants.
We chose 12 of the most abundant herbaceous species characteristics of three stages of the old‐field succession mentioned above. We investigated trait variation and covariation for the eight following traits: specific leaf area (SLA), leaf phosphorus (LPC), nitrogen (LNC) and carbon (LCC) concentrations, leaf dry matter content (LDMC) and leaf total phenols (TPh), all on material collected in the field; and litter decomposability (Kpot) and maximum relative growth rate (RGRmax), obtained under standardized conditions in the laboratory.
Five of these traits were significantly lower in species from the advanced successional stage. These trends were similar when comparisons were conducted either with the 12 species, or on a subset incorporating taxonomic information. LDMC was the single trait best correlated with species RGRmax and Kpot; the two latter traits were also significantly correlated with one another.
These results provide clear evidence of functional links between plant growth, leaf traits and litter decomposability. LDMC appears as a pivotal trait of living leaves related to their structural properties. It influences the quality of the litter produced, and hence species’ potential ‘after‐life effects’ on ecosystem properties.
Atomic force microscopy studies of conditioner thickness distribution and binding interactions on the hair surface
Authors: CHEN N. , BHUSHAN B. 
Published: March 2006

SummaryThe way in which common hair care products, such as conditioner, deposit onto and change hair properties is of interest in beauty care science, as these properties are closely tied to product performance. The binding interaction between conditioner and the hair surface is one of the important factors in determining the conditioner thickness distribution and consequently the proper functions of conditioner. In this study, atomic force microscopy was used to obtain the local conditioner thickness distribution, adhesive forces and effective Young's modulus mapping of various hair surfaces. The conditioner thickness was extracted by measuring the forces on the atomic force microscopy tip as it approached, contacted and pushed through the conditioner layer. The effective Young's moduli of various hair surfaces were calculated from the force distance curves using Hertz analysis. The intrinsic binding interactions between different silicones and the hair surface on the microscopic scale, as well as their effect on the effective Young's modulus of the hair, are also discussed. It was found that the effective Young's modulus of the hair is strongly affected by the binding of conditioner molecules on the hair surface.
Transient analysis of gaseous electron‐ion recombination in the environmental scanning electron microscope
Authors: MORGAN S. W. , PHILLIPS M. R. 
Published: March 2006

SummaryMost of the work carried out in relation to contrast mechanisms and signal formation in an environmental scanning electron microscope has yet to consider the time dependent aspects of image generation at a quantitative level. This paper quantitatively describes gaseous electron‐ion recombination (also known as ‘signal scavenging’) in an environmental scanning electron microscope at a transient level by utilizing the dark shadows/streaks seen in gaseous secondary electron detector images of alumina (Al2O3) immediately after a region of enhanced secondary electron emission is encountered by a scanning electron beam. The investigation firstly derives a theoretical model of gaseous electron‐ion recombination that takes into consideration transients caused by the time constant of the gaseous secondary electron detector electronics and external circuitry used to generate images. Experimental data of pixel intensity versus time of the streaks are then simulated using the model enabling the relative magnitudes of (i) ionization and recombination rates, (ii) recombination coefficients and (iii) electron drift velocities, as well as absolute values of the total time constant of the gaseous secondary electron detection system and external circuitry, to be determined as a function of microscope operating parameters such as gaseous secondary electron detector bias, sample‐electrode separation, imaging gas pressure, and scan speed. The results revealed, for the first time, the exact dependence that the effects of secondary electron‐ion recombination on signal formation has on reduced electric field and time in an environmental scanning electron microscope. Furthermore, the model implicitly demonstrated that signal loss as a consequence of field retardation due to ion space charges, although obviously present, is not the foremost phenomenon causing streaking in images, as previously thought.
Aclar discs: a versatile substrate for routine high‐pressure freezing of mammalian cell monolayers
Authors: JIMÉNEZ N. , HUMBEL B. M. , VAN DONSELAAR E. , VERKLEIJ A. J. , BURGER K. N. J. 
Published: March 2006

SummaryHigh‐pressure freezing avoids the artefacts induced by conventional chemical fixation, and, in combination with freeze‐substitution and plastic embedding, is a reliable method for the ultrastructural analysis of mammalian cell monolayers. In order to high‐pressure freeze mammalian cell monolayers, cells have to be seeded on a suitable substrate. Unfortunately, electron microscopy analysis is often hampered by poor cell growth, changes in cell morphology induced by the cell substrate or cell loss during processing. We report a method to culture, high‐pressure freeze, freeze‐substitute and plastic embed mammalian cell monolayers. The method is based on the use of Aclar, a copolymer film with properties very similar to those of tissue culture plastic. We show that Aclar discs support the normal growth and morphology of a wide variety of mammalian cell types, and form an ideal starting point for high‐pressure freezing, freeze‐substitution and plastic embedding. We present a complete protocol, which, because of its simplicity and reproducibility, provides a method suitable for the routine analysis of mammalian cell monolayers by electron microscopy and tomography.
Chromosome morphology after long‐term storage investigated by scanning near‐field optical microscopy
Authors: BAYLIS R. M. , DOAK S. H. , PARRY J. M. , DUNSTAN P. R. 
Published: March 2006

SummaryFluorescence in situ hybridization coupled with far‐field fluorescence microscopy is a commonly used technique to visualize chromosomal aberrations in diseased cells. To obtain the best possible results, chromatin integrity must be preserved to ensure optimal hybridization of fluorescence in situ hybridization probes. However, biological samples are known to degrade and storage conditions can be critical. This study concentrates its investigation on chromatin stability as a function of time following fluorescence in situ hybridization type denaturing protocols. This issue is extremely important because chromatin integrity affects the fluorescence response of the chromosome. To investigate this, metaphase chromosome spreads of human lymphocytes were stored at both −20 and −80 °C, and were then imaged using scanning near‐field optical microscopy over a nine month period. Using the scanning near‐field optical microscope's topography mode, chromosome morphology was analysed before and after the application of fluorescence in situ hybridization type protocols, and then as a function of storage time. The findings revealed that human chromosome samples can be stored at −20 °C for short periods of time (∼ several weeks), but storage over 3 months compromises chromatin stability. Topography measurements clearly show the collapse of the stored chromatin, with variations as large as 60 nm across a chromosome. However, storage at −80 °C considerably preserved the integrity with variations in topography significantly reduced. We report studies of the fluorescent response of stored chromosomes using scanning near‐field optical microscopy and their importance for gaining further understanding of chromosomal aberrations.
Compression along the northern Apennines? Evidence from the Mw 5.3 Monghidoro earthquake
Authors: Piccinini D. , Chiarabba C. , Augliera P. ,   Monghidoro Earthquake Group (M.E.G.)
Published: March 2006

AbstractIn this paper, we present the seismological data recorded during the deployment of a dense three‐component seismic network installed a few hours after the 2003 Mw 5.3 Monghidoro earthquake, in northern Apennines. The main shock focal solutions derived from polarities distribution and body wave modelling of regional broadband data show a NE–SW striking reverse mechanism. Accurate relative locations of aftershocks and the inversion of focal mechanisms show that earthquakes occurred on a NW‐dipping backthrust within the Adria lithosphere under a NW‐trending horizontal compression. The observed compression is a secondary process possibly explained by differential motion within the Adriatic lithosphere. Fault geometry and kinematics is controlled by pre‐existing structures.
The Arabidopsis FLC protein interacts directly in vivo with SOC1 and FT chromatin and is part of a high‐molecular‐weight protein complex
Authors: Helliwell Chris A. , Wood Craig C. , Robertson Masumi , James Peacock W. , Dennis Elizabeth S. 
Published: March 2006

SummaryThe Arabidopsis Flowering Locus C (FLC) protein is a repressor of flowering regulated by genes in the autonomous and vernalization pathways. Previous genetic and transgenic data have suggested that FLC acts by repressing expression of the floral integrator genes SOC1 and FT. We have taken an in vivo approach to determine whether the FLC protein interacts directly with potential DNA targets. Using chromatin immunoprecipitation, we have shown that FLC binds to a region of the first intron of FT that contains a putative CArG box, and have confirmed that FLC binds to a CArG box in the promoter of the SOC1 gene. MADS box proteins are thought to bind their DNA targets as dimers or higher‐order multimers. We have shown that FLC is a component of a multimeric protein complex in vivo and that more than one FLC polypeptides can be present in the complex.
Intracellular K+ sensing of SKOR, a Shaker‐type K+ channel from Arabidopsis
Authors: Liu Kun , Li Legong , Luan Sheng 
Published: March 2006

SummaryMost K+ channels in plants are structurally classified into the Shaker family named after the shaker K+ channel in Drosophila. Plant K+ channels function in many physiological processes including osmotic regulation and K+ nutrition. An outwardly rectifying K+ channel, SKOR, mediates the delivery of K+ from stelar cells to the xylem in the roots, a critical step in the long‐distance distribution of K+ from roots to the upper parts of the plant. Here we report that SKOR channel activity is strictly dependent on intracellular K+ concentrations. Activation by K+ did not affect the kinetics of voltage dependence in SKOR, indicating that a voltage‐independent gating mechanism underlies the K+ sensing process. Further analysis showed that the C‐terminal non‐transmembrane region of the SKOR protein was required for this sensing process. The intracellular K+ sensing mechanism couples SKOR activity to K+ nutrition status in the ‘source cells’, thereby establishing a supply‐based unloading system for the regulation of K+ distribution.