bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of invertebrate herbivory in grasslands depends on plant species diversity
Authors: Stein Claudia , Unsicker Sybille B. , Kahmen Ansgar , Wagner Markus , Audorff Volker , Auge Harald , Prati Daniel , Weisser Wolfgang W. 
Published: June 2010

Invertebrate herbivores are ubiquitous in most terrestrial ecosystems, and theory predicts that their impact on plant community biomass should depend on diversity and productivity of the associated plant communities. To elucidate general patterns in the relationship between invertebrate herbivory, plant diversity, and productivity, we carried out a long‐term herbivore exclusion experiment at multiple grassland sites in a mountainous landscape of central Germany. Over a period of five years, we used above‐ and belowground insecticides as well as a molluscicide to manipulate invertebrate herbivory at 14 grassland sites, covering a wide range of plant species diversity (13–38 species/m2) and aboveground plant productivity (272–1125 g·m−2·yr−1), where plant species richness and productivity of the sites were not significantly correlated.Herbivore exclusion had significant effects on the plant communities: it decreased plant species richness and evenness, and it altered plant community composition. In particular, exclusion of belowground herbivores promoted grasses at the expense of herbs. In contrast to our expectation, herbivore effects on plant community biomass were not influenced by productivity. However, effect size of invertebrate herbivores was negatively correlated with plant diversity of the grasslands: the effect of herbivory on biomass tended to be negative at sites of high diversity and positive at sites of low diversity. In general, the effects of aboveground herbivores were relatively small as compared to belowground herbivores, which were important drivers of plant community composition. Our study is the first to show that variation in the effects of invertebrate herbivory on plant communities across a landscape is significantly influenced by plant species richness.
Many routes lead to Rome: potential causes for the multi‐route migration system of Red Knots, Calidris canutus islandica
Authors: Bauer Silke , Ens Bruno J. , Klaassen Marcel 
Published: June 2010

Migrants, such as birds or representatives of other taxa, usually make use of several stopover sites to cover the distance between their site of origin and destination. Potentially, multiple routes exist, but often little is known about the causes and consequences of alternative migration routes. Apart from their geographical distribution, the suitability of potential sites might play an important role in the animals' decisions for a particular itinerary.We used an optimal‐migration model to test three nonmutually exclusive hypotheses leading to variations in the spring migration routes of a subspecies of Red Knot, Calidris canutus islandica, which migrates from wintering grounds in Western Europe to breeding grounds in Greenland and the Canadian Arctic: the breeding location hypothesis, the energy budget hypothesis, and the predation risk hypothesis. Varying only breeding location, the model predicted that birds breeding in the Canadian Arctic and on West Greenland stop over on Iceland, whereas birds breeding in East and Northeast Greenland migrate via northern Norway, a prediction that is supported by empirical findings. Energy budgets on stopover sites had a strong influence on the choice of route and staging times. Varying foraging‐intensity and mass‐dependent predation risk prompted the birds to use less risky sites, if possible. The effect of simultaneous changes in the energy budget and predation risk strongly depended on the site where these occurred.Our findings provide potential explanations for the observations that C. canutus islandica uses a diverse array of migration routes. Scrutinizing the three alternative driving forces for the choice of migratory routes awaits further, specific data collection in rapidly developing fields of research (e.g., predation risk assessment, GPS tracking). Generally, the type of modeling presented here may not only highlight alternative explanations, but also direct follow‐up empirical research.
Survival Analysis on Pedigrees: A Marked Point Process Model
Authors: Macdonald Angus S. 
Published: June 2010

AbstractRegulation of insurers' use of genetic information means actuaries are interested in age-at-onset of genetic disorders. Arjas & Haara (1984) suggested marked point processes (MPPs) as useful models for life history data with complex covariates. Age-at-onset distributions (or equivalently, hazard rates) in respect of inherited disorders are often estimated from pedigrees, which are life histories with unusually complex covariates, as well as strong dependencies induced by shared genes. Since Elston (1973) parametric models have often been used, conditioning the likelihood on known genotypes. However, a genotype identii ed by a presymptomatic genetic test is a form of internal covariate (Kalbfleisch & Prentice, 2002). We propose a very general MPP model of a pedigree, including presymptomatic genetic testing, (‘the full model’) and show under what circumstances the partial model leading to Elston's likelihood is valid. In practice, pedigrees are often ascertained retrospectively. Many such events can be modelled by augmenting the natural filtration of the MPP. We show that, except in simple special cases, the partial model is no longer valid, and the resulting likelihoods appear to be intractable. In particular, ascertainment interacts even with independent censoring so that likelihoods no longer factorize. For one simple special case — studies of sibships — we generalise a classical result to age-at-onset data. We conclude that the study of genetic conditions with variable age at onset gains insights from the underlying principles of survival analysis in their modern form, but that great care is needed in translating epidemiological studies into actuarial models.
On the Risk-Neutral Valuation of Life Insurance Contracts with Numerical Methods in View
Authors: Bauer Daniel , Bergmann Daniela , Kiesel Rüdiger 
Published: June 2010

AbstractIn recent years, market-consistent valuation approaches have gained an increasing importance for insurance companies. This has triggered an increasing interest among practitioners and academics, and a number of specific studies on such valuation approaches have been published.In this paper, we present a generic model for the valuation of life insurance contracts and embedded options. Furthermore, we describe various numerical valuation approaches within our generic setup. We particularly focus on contracts containing early exercise features since these present (numerically) challenging valuation problems.Based on an example of participating life insurance contracts, we illustrate the different approaches and compare their efficiency in a simple and a generalized Black-Scholes setup, respectively. Moreover, we study the impact of the considered early exercise feature on our example contract and analyze the influence of model risk by additionally introducing an exponential Lévy model.
Optimal Risk Control for The Excess of Loss Reinsurance Policies
Authors: Meng Hui , Zhang Xin 
Published: June 2010

AbstractThe primary objective of the paper is to explore using reinsurance as a risk management tool for an insurance company. We consider an insurance company whose surplus can be modeled by a Brownian motion with drift and that the surplus can be invested in a risky or riskless asset. Under the above Black-Scholes type framework and using the objective of minimizing the ruin probability of the insurer, we formally establish that the excess-of-loss reinsurance treaty is optimal among the class of plausible reinsurance treaties. We also obtain the optimal level of retention as well as provide an explicit expression of the minimal probability of ruin.
A Bootstrap Test for the Probability of Ruin in the Compound Poisson Risk Process
Authors: Baumgartner Benjamin , Gatto Riccardo 
Published: June 2010

AbstractIn this article we propose a bootstrap test for the probability of ruin in the compound Poisson risk process. We adopt the P-value approach, which leads to a more complete assessment of the underlying risk than the probability of ruin alone. We provide second-order accurate P-values for this testing problem and consider both parametric and nonparametric estimators of the individual claim amount distribution. Simulation studies show that the suggested bootstrap P-values are very accurate and outperform their analogues based on the asymptotic normal approximation.
Dispersion Estimates for Poisson and Tweedie Models
Authors: Rosenlund Stig 
Published: June 2010

AbstractAs a consequence of pointing out an ambiguity in Renshaw (1994), we show that the Overdispersed Poisson model cannot be generated by random independent intensities. Hence Pearson's chi-square-based estimate is normally unsuitable for GLM (Generalized Linear Model) log link claim frequency analysis in insurance. We propose a new dispersion parameter estimate in the GLM Tweedie model for risk premium. This is better than the Pearson estimate, if there are sufficiently many claims in each tariff cell. Simulation results are given showing the differences between it and the Pearson estimate.
Matrix-Form Recursions for a Family of Compound Distributions
Authors: Wu Xueyuan , Li Shuanming 
Published: June 2010

AbstractIn this paper, we aim to evaluate the distribution of the aggregate claims in the collective risk model. The claim count distribution is firstly assumed to belong to a generalised (a, b, 0) family. A matrix form recursive formula is then derived to evaluate the related compound distribution when individual claim amounts follow a discrete distribution on non-negative integers. The corresponding formula is also given for continuous individual claim amounts. Secondly, we pay particular attention to the recursive formula for compound phase-type distributions, since only certain types of discrete phase-type distributions belong to the generalised (a, b, 0) family. Similar recursive formulae are obtained for discrete and continuous individual claim amount distributions. Finally, numerical examples are presented for three counting distributions.
Numerical Evaluation of Continuous Time Ruin Probabilities for a Portfolio with Credibility Updated Premiums
Authors: Afonso Lourdes B. , Reis Alfredo D. Egídio dos , Waters Howard R. 
Published: June 2010

AbstractThe probability of ruin in continuous and finite time is numerically evaluated in a classical risk process where the premium can be updated according to credibility models and therefore change from year to year. A major consideration in the development of this approach is that it should be easily applicable to large portfolios. Our method uses as a first tool the model developed by Afonso et al. (2009), which is quite flexible and allows premiums to change annually. We extend that model by introducing a credibility approach to experience rating.We consider a portfolio of risks which satisfy the assumptions of the Bühlmann (1967, 1969) or Bühlmann and Straub (1970) credibility models. We compute finite time ruin probabilities for different scenarios and compare with those when a fixed premium is considered.
The Effect of an Old-Age Demogrant on the Labor Supply and Time Use of the Elderly and Non-Elderly in Mexico
Authors: Juarez Laura 
Published: June 2010

Abstract
This paper estimates the effect of a generous demogrant for individuals age 70 and older that started in 2001 in Mexico City on the labor supply and time use of beneficiaries and of non-elderly family members who live with them. Using a triple differences approach, I find that the program has no significant effect on the time use of eligible individuals, except for the sharp decrease in the housework participation of elderly women who live with another potential beneficiary. Individuals 60 to 69 years old change their time use only if they live with a potential beneficiary, but not because they expect to receive the demogrant themselves in a few years. In particular, men in their 60s seem to retire early if they live with someone who qualifies for the transfer. Both men and women 18 to 59 years old increase their labor supply if they live with an eligible man, but decrease it if they live with an eligible woman. These results are consistent with income in the hands of elderly women being shared more with younger family members than income in the hands of elderly men.
Mesenchymal Bone Morphogenetic Protein Signaling Is Required for Normal Pancreas Development
Authors: Ahnfelt-Rønne Jonas , Ravassard Philippe , Pardanaud-Glavieux Corinne , Scharfmann Raphaél , Serup Palle 
Published: June 2010

OBJECTIVE
Pancreas organogenesis is orchestrated by interactions between the epithelium and the mesenchyme, but these interactions are not completely understood. Here we investigated a role for bone morphogenetic protein (BMP) signaling within the pancreas mesenchyme and found it to be required for the normal development of the mesenchyme as well as for the pancreatic epithelium.

RESEARCH DESIGN AND METHODS
We analyzed active BMP signaling by immunostaining for phospho-Smad1,5,8 and tested whether pancreas development was affected by BMP inhibition after expression of Noggin and dominant negative BMP receptors in chicken and mouse pancreas.

RESULTS
Endogenous BMP signaling is confined to the mesenchyme in the early pancreas and inhibition of BMP signaling results in severe pancreatic hypoplasia with reduced epithelial branching. Notably, we also observed an excessive endocrine differentiation when mesenchymal BMP signaling is blocked, presumably secondary to defective mesenchyme to epithelium signaling.

CONCLUSIONS
We conclude that BMP signaling plays a previously unsuspected role in the mesenchyme, required for normal development of the mesenchyme as well as for the epithelium.
Local Expression of Indoleamine 2,3 Dioxygenase in Syngeneic Fibroblasts Significantly Prolongs Survival of an Engineered Three-Dimensional Islet Allograft
Authors: Jalili Reza B. , Forouzandeh Farshad , Rezakhanlou Alireza Moeen , Hartwell Ryan , Medina Abelardo , Warnock Garth L. , Larijani Bagher , Ghahary Aziz 
Published: June 2010

OBJECTIVEThe requirement of systemic immunosuppression after islet transplantation is of significant concern and a major drawback to clinical islet transplantation. Here, we introduce a novel composite three-dimensional islet graft equipped with a local immunosuppressive system that prevents islet allograft rejection without systemic antirejection agents. In this composite graft, expression of indoleamine 2,3 dioxygenase (IDO), a tryptophan-degrading enzyme, in syngeneic fibroblasts provides a low-tryptophan microenvironment within which T-cells cannot proliferate and infiltrate islets.RESEARCH DESIGN AND METHODSComposite three-dimensional islet grafts were engineered by embedding allogeneic mouse islets and adenoviral-transduced IDO–expressing syngeneic fibroblasts within collagen gel matrix. These grafts were then transplanted into renal subcapsular space of streptozotocin diabetic immunocompetent mice. The viability, function, and criteria for graft take were then determined in the graft recipient mice.RESULTSIDO-expressing grafts survived significantly longer than controls (41.2 ± 1.64 vs. 12.9 ± 0.73 days; P &lt; 0.001) without administration of systemic immunesuppressive agents. Local expression of IDO suppressed effector T-cells at the graft site, induced a Th2 immune response shift, generated an anti-inflammatory cytokine profile, delayed alloantibody production, and increased number of regulatory T-cells in draining lymph nodes, which resulted in antigen-specific impairment of T-cell priming.CONCLUSIONSLocal IDO expression prevents cellular and humoral alloimmune responses against islets and significantly prolongs islet allograft survival without systemic antirejection treatments. This promising finding proves the potent local immunosuppressive activity of IDO in islet allografts and sets the stage for development of a long-lasting nonrejectable islet allograft using stable IDO induction in bystander fibroblasts.
Increased Cytochrome P4502E1 Expression and Altered Hydroxyeicosatetraenoic Acid Formation Mediate Diabetic Vascular Dysfunction
Authors: Schäfer Andreas , Galuppo Paolo , Fraccarollo Daniela , Vogt Christian , Widder Julian D. , Pfrang Julia , Tas Piet , Barbosa-Sicard Eduardo , Ruetten Hartmut , Ertl Georg , Fleming Ingrid , Bauersachs Johann 
Published: June 2010

OBJECTIVE
We investigated the mechanisms underlying vascular endothelial and contractile dysfunction in diabetes as well as the effect of HMR1766, a novel nitric oxide (NO)-independent activator of soluble guanylyl cyclase (sGC).

RESEARCH DESIGN AND METHODS
Two weeks after induction of diabetes by streptozotocin, Wistar rats received either placebo or HMR1766 (10 mg/kg twice daily) for another 2 weeks; thereafter, vascular function was assessed.

RESULTS
Endothelial function and contractile responses were significantly impaired, while vascular superoxide formation was increased in the aortae from diabetic versus healthy control rats. Using RNA microarrays, cytochrome P4502E1 (CYP2E1) was identified as the highest upregulated gene in diabetic aorta. CYP2E1 protein was significantly increased (16-fold) by diabetes, leading to a reduction in levels of the potent vasoconstrictor 20-hydroxy-eicosatetraenoic acid (20-HETE). Induction of CYP2E1 expression in healthy rats using isoniazide mimicked the diabetic noncontractile vascular response while preincubation of aortae from STZ-diabetic rats in vitro with 20-HETE rescued contractile function. Chronic treatment with the sGC activator HMR1766 improved NO sensitivity and endothelial function, reduced CYP2E1 expression and superoxide formation, enhanced 20-HETE levels, and reversed the contractile deficit observed in the diabetic rats that received placebo.

CONCLUSIONS
Upregulation of CYP2E1 is essentially involved in diabetic vascular dysfunction. Chronic treatment with the sGC activator HMR1766 reduced oxidative stress, decreased CYP2E1 levels, and normalized vasomotor function in diabetic rats.
Tauroursodeoxycholic Acid May Improve Liver and Muscle but Not Adipose Tissue Insulin Sensitivity in Obese Men and Women
Authors: Kars Marleen , Yang Ling , Gregor Margaret F. , Mohammed B. Selma , Pietka Terri A. , Finck Brian N. , Patterson Bruce W. , Horton Jay D. , Mittendorfer Bettina , Hotamisligil Gökhan S. , Klein Samuel 
Published: June 2010

OBJECTIVE
Insulin resistance is commonly associated with obesity. Studies conducted in obese mouse models found that endoplasmic reticulum (ER) stress contributes to insulin resistance, and treatment with tauroursodeoxycholic acid (TUDCA), a bile acid derivative that acts as a chemical chaperone to enhance protein folding and ameliorate ER stress, increases insulin sensitivity. The purpose of this study was to determine the effect of TUDCA therapy on multiorgan insulin action and metabolic factors associated with insulin resistance in obese men and women.

RESEARCH DESIGN AND METHODS
Twenty obese subjects ([means ± SD] aged 48 ± 11 years, BMI 37 ± 4 kg/m2) were randomized to 4 weeks of treatment with TUDCA (1,750 mg/day) or placebo. A two-stage hyperinsulinemic-euglycemic clamp procedure in conjunction with stable isotopically labeled tracer infusions and muscle and adipose tissue biopsies were used to evaluate in vivo insulin sensitivity, cellular factors involved in insulin signaling, and cellular markers of ER stress.

RESULTS
Hepatic and muscle insulin sensitivity increased by ∼30% (P &lt; 0.05) after treatment with TUDCA but did not change after placebo therapy. In addition, therapy with TUDCA, but not placebo, increased muscle insulin signaling (phosphorylated insulin receptor substrateTyr and AktSer473 levels) (P &lt; 0.05). Markers of ER stress in muscle or adipose tissue did not change after treatment with either TUDCA or placebo.

CONCLUSIONS
These data demonstrate that TUDCA might be an effective pharmacological approach for treating insulin resistance. Additional studies are needed to evaluate the target cells and mechanisms responsible for this effect.
Growth, ion composition, and stomatal conductance of peas exposed to salinity
Authors: Maksimović Ivana , Putnik-Delić Marina , Gani Ivana , Marić Jovana , Ilin Žarko 
Published: June 2010

Abstract
Availability of irrigation water of appropriate quality is becoming critical in many regions. Excess salt in irrigation water represents a risk for crop yield, crop quality, and soil properties. During the short vegetation period, field peas require high amounts of water, and irrigation is often indispensable for successful production. Steady presence of NaCl (0.1, 0.2, 0.6 or 1.2 g NaCl L−1 in 1/2 strength Hoagland nutrient solution) under semi-controlled conditions reduced growth and resulted in shorter vegetation. Disturbances in the peas’ water regime were provoked by NaCl, as water content in pea tissues was reduced and stomatal density and stomatal diffusive resistance increased in the presence of higher NaCl concentrations. Concentration of Na+ increased in all pea tissues with increased NaCl concentration in the nutrient medium. In the presence of NaCl, concentrations of K+, Ca2+ and Pi increased in roots, stems and leaves, and decreased and in pods and grains. Concentration ratios Na+/K+, Na+/Ca2+, K+/Ca2+ and (Na++K+)/Ca2+ in various plant parts were affected as well, but magnitudes of changes were variable. Continuous presence of NaCl in concentrations frequently met in irrigation waters significantly reduced pea growth, impaired the water regime, and altered plant chemical composition.
Switching p53-dependent growth arrest to apoptosis via the inhibition of DNA damage-activated kinases
Authors: Hublarova Pavla , Greplova Kristina , Holcakova Jitka , Vojtesek Borivoj , Hrstka Roman 
Published: June 2010

AbstractCisplatin and doxorubicin are widely used anticancer drugs that cause DNA damage, which activates the ATM-Chk2-p53 pathway in cancer cells. This activation leads to cell cycle block or apoptosis, depending on the nature of the DNA damage. In an attempt to enhance the effects of these agents, we inhibited ATM/ATR and Chk2, which are known upstream regulators of p53. The cancer cell lines A2780 and ARN8, bearing the wild-type p53 protein, were used to study changes in p53 activation and trans-activation. Our results suggest that the G1-checkpoint, normally activated by DNA damage, is functionally overcome by the action of kinase inhibitors that sensitize cells to apoptosis. Both inhibitors show these effects, albeit with variable intensity in different cell lines, which is promising for other studies and theoretically for use in clinical practice.