bluuebunny/crossref_metadata_2025_split huggingface dataset:
Potential effects of earthworms on leaf‐chewer performance
Authors: NEWINGTON J. E. , SETÄLÄ H. , BEZEMER T. M. , JONES T. H. 
Published: September 2004

Summary

Detritivores affect plant performance and therefore have the potential indirectly to affect above‐ground herbivore populations.
In a microcosm study we asked whether changes in the performance of two plant species, Cardamine hirsuta L. and Veronica persica Poiret., arising from the activity of various earthworm communities influenced the consumption rate and development of a leaf‐chewer, Mamestra brassicae L.
Earthworms increased soil nitrate and foliar nitrogen concentrations. There was no associated increase in plant biomass.
There was no significant effect of earthworm treatment on the biomass of M. brassicae larvae. However, highest larval mortality occurred in microcosms without earthworms, while the proportion of larvae that had reached the final instar was lowest. In a 24 h feeding trial, the consumption rate of V. persica foliage by M. brassicae was higher when plants were grown in soil containing earthworms. The complexity of earthworm communities did not affect M. brassicae consumption rates and consequent development.
This is the first study to show the potential of detritivore communities indirectly to affect leaf‐chewing herbivores. It highlights the need to explore the interactions that occur between above‐ and below‐ground components of plant–insect communities.
Increased photosynthetic performance in holly trees infested by scale insects
Authors: RETUERTO R. , FERNANDEZ‐LEMA B. , RODRIGUEZ‐ROILOA  , OBESO J. R. 
Published: September 2004

Summary

Changes in plant physiological features after herbivory may alleviate the adverse effects of herbivores. We examined the ability of Ilex aquifolium L. (European Holly) plants to compensate for scale insect herbivory through increased photosynthesis. Based on assumptions of the source–sink hypothesis, we predicted that scale insects, by inducing supplementary sinks for photosynthates, would increase photosynthesis.
Photosynthetic performance was evaluated by measuring chlorophyll fluorescence parameters in plants growing under natural light and temperature at the field station of the University of Santiago (north‐west Spain). We measured photosynthesis on infested leaves of infested trees; scale‐free leaves of infested trees; and scale‐free leaves of scale‐free trees.
Insect infestation significantly increased photosynthetic efficiency. Effects of scale insects on photosynthesis were particularly enhanced by high temperature and light. Scale insects also altered the photosynthesis of leaves not directly affected by the insects.
Our study showed that changes in the balance between source and sink tissues, induced by scale insects, may partly explain host plant photosynthesis. We suggest that increased feeding rates of scale insects promoted by high temperature and light conditions would increase the carbon demand of infested plants, resulting in greater compensatory photosynthesis.
Estimating endogenous nutrient allocations to reproduction in Redhead Ducks: a dual isotope approach using δD and δ13C measurements of female and egg tissues
Authors: HOBSON K. A. , ATWELL L. , WASSENAAR L. I. , YERKES T. 
Published: September 2004

Summary

Clutch formation represents a considerable energy expense for waterfowl, yet little evidence is available to quantify nutrient allocation from endogenous and exogenous sources. Here we investigated hydrogen and carbon stable isotope ratios (δD and δ13C) in female Redhead Ducks (Aythya americana) and their eggs to evaluate the use of δD as an indicator of nutrient sources to reproduction.
Females arrived with mean muscle tissue δD and δ13C values more positive than those of the local food web, reflecting marine dietary inputs from the wintering grounds. These values changed to the range of local food values by late incubation. δ13C values from albumen and yolk protein were correlated, supporting the presence of a common exogenous carbon source for these egg components.
There was no significant correlation between δD or δ13C values in egg tissues and abdominal fat or muscle from the corresponding laying female. No general population‐level trends in isotope values from sequentially developing follicle yolks were found.
Redhead females relied mainly on dietary lipids and proteins for egg production, and therefore endogenous reserves were used to satisfy female body maintenance and energy requirements.
Evolutionary changes in nectar sugar composition associated with switches between bird and insect pollination: the Canarian bird‐flower element revisited
Authors: DUPONT Y. L. , HANSEN D. M. , RASMUSSEN J. T. , OLESEN J. M. 
Published: September 2004

Summary

The bird‐flower element of the Canary Islands is a group of endemic plants having traits characteristic of bird pollination, and some are visited by opportunistically nectar‐feeding passerine birds.
We investigated evolutionary changes in nectar sugar composition in seven Canarian lineages of ornithophilous plant species and their entomophilous relatives.
We hypothesized that nectar sugar composition evolved in response to the main pollinator group of a plant. Specialist nectarivores can assimilate sucrose, whereas some opportunistic nectar‐feeders digest only the simple hexoses.
Sugar composition of nectars was analysed using high pH anion exchange chromatography.
Evolution of nectar type was correlated with mode of pollination. Generally, sucrose nectars were associated with insect visitation and hexose nectars with bird visitation. Nectar sugar composition was an evolutionary labile trait within a lineage. Hence, nectar characteristics may have evolved readily, perhaps in response to opportunistically nectarivorous birds living in the Canary Islands.
Soil animals influence microbial abundance, but not plant–microbial competition for soil organic nitrogen
Authors: COLE L. , STADDON P. L. , SLEEP D. , BARDGETT R. D. 
Published: September 2004

SummaryIn a microcosm experiment we examined the effects of individual species of microarthropods, and variations in microarthropod diversity of up to eight species, on soil microbial properties and the short‐term partitioning of a dual‐labelled organic nitrogen source (glycine‐2‐13C‐15N) between a grassland plant,Agrostis capillaris, and the soil microbial biomass, to determine how soil fauna and their diversity influence plant–microbial competition for organic N.We hypothesized that variations in the diversity of animals would influence the partitioning of15N inputs between plants and the microbial biomass, due to the effect of animal grazing on the microbial biomass, and hence its ability to sequester N.Certain individual species of Collembola influenced the microbial community of the soil.Folsomia quadrioculatareduced microbial biomass, whereasMesaphorura macrochaetaenhanced arbuscular mycorrhizal (AM) colonization ofA. capillarisroots. Effects of increasing species richness of microarthropods on microbial biomass and AM colonization were detected, but these effects could be interpreted in relation to the presence or absence of individual species.Microbial uptake of added15N was not affected by the presence of any of the individual species of animal in the monoculture treatments. Similarly, increasing diversity of microarthropods had no detectable effect on microbial15N.Root and shoot uptake of15N was also largely unaffected by both single species and variations in diversity of microarthropods. However, one collembolan species,Ceratophysella denticulata, reduced root15N capture when present in monoculture. We did not detect13C in plant tissue under any experimental treatments, indicating that all N was taken up by plants after mineralization.Our data suggest that, while single species and variations in diversity of microarthropods influence microbial abundance in soil, there is no effect on microbial or plant uptake of N. Overall, these data provide little support for the notion that microbial‐feeding soil animals are regulators of microbial–plant competition for N.
A new method for calculating volume of excavated burrows: the geomorphic impact of Wedge‐Tailed Shearwater burrows on Rottnest Island
Authors: BANCROFT W. J. , HILL D. , ROBERTS J. D. 
Published: September 2004

SummaryStudies of ecosystem engineering may use burrow volume and soil displacement rate to quantify the impact of burrowing vertebrates. Calculations of burrow volume from morphometric measurements have previously treated burrows as rectangular or elliptical prisms.Here we use burrows of the Wedge‐Tailed Shearwater (Puffinus pacificusGmelin, 1789) to demonstrate a new method for collecting morphometric data, and for mathematically modelling burrow shape used to calculate burrow volume.Our method improves on previous estimates by better estimating the cross‐sectional burrow shape, and by accounting for some of the variation in burrow width and height.Wedge‐Tailed Shearwater burrows were parabolic in cross‐section, averaged 1·99 ± 0·04SE m in length and had a mean volume of 0·06 ± 0·00SE m3. The shearwaters excavate at a rate of 7·75 m3 ha−1 year−1(10·51 t ha−1 year−1) which ranks them above many geomorphic mammals. We suggest that this warrants further investigation into the role of burrowing seabirds as ecosystem engineers.
Maternal antibody transmission and breeding densities in the Black‐headed GullLarus ridibundus
Authors: MÜLLER WENDT , GROOTHUIS TON G. G. , DIJKSTRA COR , SIITARI HELI , ALATALO RAUNO V. 
Published: September 2004

SummaryThe offspring of avian species, especially those of colonial breeders, are exposed to a number of pathogens immediately after birth. The chick's immune system is, at that early stage still immature and inefficient. As a consequence, diseases can have a strong impact on chick survival.The ability of mothers to transmit passive immunity in terms of antibodies of their own acquired immunity to their chicks is probably an essential pathway to enhance the chick survival. Since the production of antibodies is costly, females are expected to adjust the transmission of passive immunity to the local disease environment.We found that in Black‐headed Gulls (Larus ridibundusL.) yolk antibody concentrations are positively correlated with local breeding density. This transmission pattern is likely to be adaptive, as the aggregation of birds will enhance the local presence of pathogens.When birds were forced to re‐settle after the colony had been flooded (10–20% of the original number of breeding pairs re‐settled), this relationship was no longer present. The lack of such a relationship may be explained by the fact that females may retain certain levels of antibodies as a consequence of infections that occurred during the first breeding attempt at a different breeding density.Within clutches, maternal antibodies decreased with laying sequence, in particular in eggs hatching male chicks. This transmission pattern may contribute to the observed mortality pattern found in gull species.
Growth efficiency and temperature in scallops: a comparative analysis of species adapted to different temperatures
Authors: HEILMAYER O. , BREY T. , PÖRTNER H. O. 
Published: September 2004

SummaryData were collected on metabolic activity and growth in pectinid bivalves from published studies. The resulting database comprised three types of data sets: (i) synoptic data (13 populations, 7 species), where both individual growth performance and metabolism are known, (ii) ‘metabolism only’ data (82 populations, 13 species), and (iii) ‘growth only’ data (198 populations, 26 species).In pectinid bivalves belonging to different species and living under different environmental conditions metabolic activity (standard metabolic rate, SMRAvg,Q10 = 2·97) is more closely related to temperature than individual growth (overall growth performance, OGP index P,Q10 = 1·12).The synthesis of the two corresponding Arrhenius equations shows that the relationship between the SMRAvg‐to‐OGP ratio and temperature follows the Arrhenius model, too, withQ10 = 2·26.SMRAvg‐to‐OGP is an inverse proxy for growth efficiency, hence growth efficiency decreases with rising temperature across a wide range of pectinid populations and species. Thus, there is strong empirical evidence that elevated temperature constrains growth efficiency in scallops and that adaptation does not fully compensate for this effect.
Increased haemolymph osmolality suggests a new route for behavioural manipulation ofTalorchestia quoyana(Amphipoda: Talitridae) by its mermithid parasite
Authors: WILLIAMS C. M. , POULIN R. , SINCLAIR B. J. 
Published: September 2004

SummaryHairworms (phylum Nematomorpha) and mermithid nematodes (phylum Nematoda) have independently evolved almost identical life cycles: both parasites cause their terrestrial arthropod hosts to seek water, required for their aquatic free‐living adult stage. Hairworms achieve this by altering host neurotransmitters, but the mechanisms used by mermithids remain unknown.The physiological effects of the mermithid nematodeThaumamermis zealandicaon its host, the supralittoral talitrid amphipodTalorchestia quoyana, are investigated. The parasite develops in the haemocoel, and induces the host to burrow more deeply than healthy amphipods and the adultT. zelandicaemerges from the host into moist sand at these greater depths.Parasitized amphipods had higher haemolymph osmolality than unparasitized amphipods. There was no difference in haemolymph Na+, K+or Mg2+concentrations between parasitized and unparasitized amphipods.Water content did not differ between parasitized and unparasitized amphipods. Lipid reserves were lower in parasitized male amphipods than in unparasitized males; there was no difference among females.Increase of host haemolymph osmolality byT. zealandicacould induce ‘thirst’, explaining why parasitized amphipods seek water‐saturated sand. This mechanism appears more parsimonious than that used by nematomorphs to achieve the same change in host behaviour.
Default Recovery Rates in Credit Risk Modelling: A Review of the Literature and Empirical Evidence
Authors: Altman Edward , Resti Andrea , Sironi Andrea 
Published: September 2004

Evidence from many countries in recent years suggests that collateral values and recovery rates (RRs) on corporate defaults can be volatile and, moreover, that they tend to go down just when the number of defaults goes up in economic downturns. This link between RRs and default rates has traditionally been neglected by credit risk models, as most of them focused on default risk and adopted static loss assumptions, treating the RR either as a constant parameter or as a stochastic variable independent from the probability of default (PD). This traditional focus on default analysis has been partly reversed by the recent significant increase in the number of studies dedicated to the subject of recovery‐rate estimation and the relationship between default and RRs. This paper presents a detailed review of the way credit risk models, developed during the last 30 years, treat the RR and, more specifically, its relationship with the PD of an obligor. Recent empirical evidence concerning this issue is also presented and discussed. (J.E.L.: G15, G21, G28).
The Co‐initial Swap Market Model
Authors: Galluccio Stefano , Hunter Christopher 
Published: September 2004

In this paper, we introduce a novel approach to the pricing and the risk management of generic European style interest‐rate derivatives. This new model has great flexibility and has the advantage of avoiding complex model calibration techniques typical of standard short‐rate models. Dynamics is assigned on a set of co‐initial forward swap rates, and arbitrage‐free restrictions are determined in a normal and lognormal setup. Model implementation and calibration are discussed, and details of two example applications are also presented. (J.E.L.: G12, G13).
Preventing Systemic Crises through Bank Transparency
Authors: Hyytinen Ari , Takalo Tuomas 
Published: September 2004

The banking system is known to be vulnerable to self‐fulfilling crises that are caused by depositors’ co‐ordination failure. We show that transparency regulation may prevent certain types of systemic crisis by eliminating the possibility of coordination failure. (J.E.L.: G21, G28).
Pricing and Informational Efficiency of the MIB30 Index Options Market. An Analysis with High‐frequency Data
Authors: Cassese Gianluca , Guidolin Massimo 
Published: September 2004

We analyse the pricing and informational efficiency of the Italian market for options written on the most important stock index, the MIB30. We report that a striking percentage of the data consists of option prices violating basic no‐arbitrage conditions. This percentage declines when we relax the no‐arbitrage restrictions to accommodate the presence of bid/ask spreads and other frictions but never becomes negligible. We also investigate the informational efficiency of the MIBO and conclude that option prices are poor predictors of the volatility of MIB30 returns. This conclusion is robust to a number of statistical and sampling methods. (J.E.L.: G13, G14).
Cytochrome c oxidase as the target of the heat shock protective effect in septic liver
Authors: Chen Hsiang‐Wen , Kuo Hung‐Tien , Lu Tzong‐Shi , Wang Shu‐Jung , Yang Rei‐Cheng 
Published: September 2004

SummaryLiver function failure is one of the characteristics of critically ill, septic patients and is associated with worse outcome. Our previous studies have demonstrated that heat‐shock response protects cells and tissue from subsequent insults and improves survival during sepsis. In this study, we have shown that mitochondrial cytochrome c oxidase (CCO) is one of the major sources of that protective effect. Experimental sepsis was induced by the cecal ligation and puncture (CLP) method. Heat‐shock treatment was induced in rats by hyperthermia 24 h before CLP operation. The results showed that ATP content of the liver declined significantly, and the enzymatic activity of mitochondrial CCO was apparently suppressed during the late stages of sepsis. The mitochondrial ultrastructure of septic liver showed the deformity, mild swelling and inner membrane budding. Heat‐shock treatment led to heat‐shock protein 72 overexpression and prevented the downregulation of Grp75 during sepsis. On the contrary, the expression of the enzyme complex and its activity were preserved, associated with the minimization of ultrastructural deformities. In conclusion, the maintenance of mitochondrial function, especially the CCO, may be an important strategy in therapeutic interventions of a septic liver.
Liver portal fibrosis in dioxin receptor‐null mice that overexpress the latent transforming growth factor‐β‐binding protein‐1
Authors: Corchero Javier , Martín‐Partido Gervasio , Dallas Sarah L. , Fernández‐Salguero Pedro M. 
Published: September 2004

SummaryMice lacking aryl hydrocarbon (dioxin) receptor (AhR) had variable degree of hepatic fibrosis and altered liver architecture. Transforming growth factor‐β (TGF‐β), a major profibrogenic molecule in the liver, is localized to the extracellular matrix by its association to the latent TGF‐β‐binding protein‐1 (LTBP‐1). Very recently, LTBP‐1 has been shown to be negatively regulated by the AhR. Embryonic fibroblasts from AhR‐null (AhR–/–) mice overexpress LTBP‐1 and secrete four times more active TGF‐β than wild‐type fibroblasts. To test whether TGF‐β and LTBP‐1 overexpression colocalize within the fibrotic nodule of AhR–/– liver, we have characterized this hepatic portal fibrosis using collagen protein staining, immunohistochemistry and in situ hybridization. LTBP‐1 mRNA and protein were overexpressed in the fibrotic region and colocalized with other indicators of fibrosis such as collagen and fibronectin and the fibroblast marker proteins α‐actin and vimentin. TGF‐β protein also colocalized with fibrosis, although in contrast, TGF‐β mRNA expression, rather than restricted to the fibrotic compartment, was present throughout the hepatic parenchyma and exhibited similar levels in wild‐type and AhR–/– mice. These results suggest that LTBP‐1 targets TGF‐β to specific areas of the liver and that the AhR could be a negative regulator of liver fibrosis, possibly through the control of LTBP‐1 and TGF‐β activities.
The effect of enalapril on the cardiac remodelling in ovariectomized spontaneously hypertensive rats
Authors: Santos Wellington V. , Pereira Leila M.M. , Mandarim‐de‐Lacerda Carlos A. 
Published: September 2004

SummaryAngiotensin‐converting enzyme inhibitors reduce the blood pressure (BP) and inhibit the generation of the angiotensin II from the inactive angiotensin I. Ten 28‐week‐old spontaneously hypertensive rats (SHRs) had their ovaries bilaterally removed and five rats were left intact and studied for 7 additional weeks: intact group, ovariectomized group (ovx SHRs) and ovariectomized + enalapril group (ovx + en). BP was higher in ovx SHRs and lower in treated ovx SHRs. Left ventricular (LV) mass index was greater in untreated ovx SHRs and smaller in ovx + en group. The LV cardiomyocyte (cmy) mean cross‐sectional area, measured by stereology, was greater in ovx SHRs and smaller in both intact and ovx + en SHRs. Ovx significantly decreased the density of intramyocardial blood vessels (ive), but administration of enalapril was able to restore the density of the ive to that seen in intact group. The worst ive:cmy ratio was found in untreated ovx SHRs, the intact group showed a 90% greater ratio, and the treated ovx group showed a 150% greater ratio than the untreated ovx group. In conclusion, ovariectomy, in SHRs, causes cardiac hypertrophy and an unfavourable myocardial remodelling. Of the spectrum of changes seen, the major effect of enalapril appears to be mediated via an increase in the density of ive.
The role of the hiatus hernia in gastro‐oesophageal reflux disease
Authors: Gordon C. , Kang J. Y. , Neild P. J. , Maxwell J. D. 
Published: September 2004

SummaryA sliding hiatus hernia disrupts both the anatomy and physiology of the normal antireflux mechanism. It reduces lower oesophageal sphincter length and pressure, and impairs the augmenting effects of the diaphragmatic crus. It is associated with decreased oesophageal peristalsis, increases the cross‐sectional area of the oesophago‐gastric junction, and acts as a reservoir allowing reflux from the hernia sac into the oesophagus during swallowing. The overall effect is that of increased oesophageal acid exposure. The presence of a hiatus hernia is associated with symptoms of gastro‐oesophageal reflux, increased prevalence and severity of reflux oesophagitis, as well as Barrett's oesophagus and oesophageal adenocarcinoma. The efficacy of treatment with proton pump inhibitors is reduced. Our view on the significance of the sliding hiatus hernia in gastro‐oesophageal reflux disease has changed enormously in recent decades. It was initially thought that a hiatus hernia had to be present for reflux oesophagitis to occur. Subsequently, the hiatus hernia was considered an incidental finding of little consequence. We now appreciate that the hiatus hernia has major patho‐physiological effects favouring gastro‐oesophageal reflux and hence contributing to oesophageal mucosal injury, particularly in patients with severe gastro‐oesophageal reflux disease.